NORTH  CAROLINA  STATE  UNIVERSITY  LIBRARIES 


S02811870  R 


This  book  is  due  on  the  date  indicated  unless 
recalled  by  the  Libraries.  Books  not  returned  on 
time  are  subject  to  replacement  charges. 
Borrowers  may  access  their  library  accounts  at: 
http://www.lib.ncsu.edu/ads/borrow.html 


THE 
CULTURE  AND  DISEASES 
OF  THE  SWEET  POTATO 


BY  THE  SAME  AUTHOR 

THE   CULTURE  AND   DISEASES 

OF  THE  SWEET  PEA 
DISEASES  OF  TRUCK   CROPS 

AND  THEIR  CONTROL 
DISEASES    OF    GREENHOUSE 

CROPS  AND  THEIR  CONTROL 

Each  fully  illustrated 


In  Preparation 

THE  ONION  AND  ITS  DISEASES 

IN  AMERICA 

THE  SOIL  IN  HEALTH  AND 

IN  DISEASE 

E.  P.  DUTTON  &  COMPANY 


THE 
CULTURE  AND  DISEASES 
OF  THE  SWEET  POTATO 


BY 
J:  J.  TAUBENHAUS,  Ph.D. 

Chief  of  Division  of  Plant  Pathology  and  Physiology,  Texas  Agricultural 

Experiment  Station.    Fellow  of  the  American  Association  for  the 

Advancement  of  Science,  Charter  Member  of  the  American 

Phytopathological  Society,  Member  of  the  American 

Botanical  Society,  Author  of  "Diseases  of 

Truck  Crops  and  their  Control,"  etc. 


NEW  YORK 
E.  P.  DUTTON  &  COMPANY 

68 1   Fifth  Avenue 


Copyright,  1923, 
By  E.  P.  DUTTON  &  COMPANY 

All  Right$  Rei$rt$d 


Printed  in  th»  United  States  of  America 


THIS  BOOK 

IS   AFFECTIONATELY  DEDICATED 

TO 


INTRODUCTION 

The  time  is  rapidly  approaching  when,  as  a  food,  the 
sweet  potato  will  share  equal  honors  with  that  of  the 
white  potato.  Although  a  tropical  plant,  its  commercial 
value  has  been  recognized  by  the  American  growers  of 
the  south  who  adopted  it  as  an  important  money  crop. 
Furthermore,  it  has  become  a  staple  food  product  in  the 
average  American  home.  The  sweet  potato  is  a  typical 
truck  crop,  thriving  best  in  light  sandy  loams.  With  this 
in  mind,  its  future  is  unlimited.  Texas  alone  possesses 
enough  typical  land  to  grow  sweet  potatoes  for  the  entire 
population  of  the  United  States.  Moreover,  many  of  the 
southern  states  such  as  Alabama,  Georgia  and  others  can 
produce  sweet  potatoes  sufficient  to  feed  the  entire 
world.  With  this  crop  rapidly  coming  into  prominence 
and  as  knowledge  of  sweet  potato  storage  increases, 
thereby  reducing  the  losses  from  rotting,  the  day  is  not 
far  distant  when  we  will  be  in  a  position  to  export  and 
to  ship  sweet  potatoes  to  many  of  the  European  and 
Asiatic  countries  where  this  crop  cannot  be  profitably 
grown  on  account  of  difference  in  soil  or  climatic  con- 
ditions. The  present  great  drawback  to  the  more  ex- 
tensive production  of  sweet  potatoes  is  its  highly 
perishable  nature,  both  in  the  field  and  in  storage.  It 
has  been  estimated  by  the  Plant  Disease  Survey  of  the 
United  States  Department  of  Agriculture  that  in  19 17 
the  loss  from  the  more  important  sweet  potato  diseases 
was  32.37  per  cent  of  the  total  crop,  or  a  net  waste  of 
41 ,706,000  bushels.    In  the  foregoing  estimate  the  losses 


viii  Introduction 

from  Texas  root  rot,  Osonium  omnivorum,  root  knot, 
Heterodera  radicicola,  and  from  various  insect  pests, 
especially  the  weevil,  were  not  considered.  These  if 
taken  into  account  would  swell  the  total  loss  to  38.19 
per  cent  or  a  waste  of  49,158,000  bushels  of  sweet 
potatoes.  In  estimating  a  general  price  of  $1.10  during 
191 7,  the  total  loss  amounted  to  $54,073,800.  During 
1918  and  19 1 9  the  acreage  of  sweet  potatoes  in  the 
United  States  was  steadily  increased  so  that  the  19 19 
crop  was  estimated  as  103,579,000  bushels.  Due  to  the 
heavy  rainfall  during  that  year,  the  loss  from  rotting, 
both  in  the  field  and  in  storage,  was  considerably  higher 
than  in  19 17,  which  a  conservative  estimate  placed 
at  45  per  cent  of  the  total  crop,  or  a  direct  waste  of 
46,610,550  bushels.  In  estimating  the  average  price  per 
bushel  in  1919  at  $1.50,  the  net  loss  to  the  American 
growers  was  $69,915,825.  It  is  doubtful  if  the  acreage 
during  the  last  few  years  has  increased  considerably 
over  that  of  191 9,  so  that  the  average  production  and 
the  loss  from  diseases  were  about  the  same  as  for  1919. 
It  is  further  doubtful  if  the  sweet  potato  acreage  will 
be  reduced  in  the  future  and  for  the  reasons  given  above 
it  is  reasonable  to  believe  that  it  will  steadily  be  in- 
creased. It  is,  therefore,  evident  that  when  an  average 
annual  loss  of  $69,915,825  is  facing  us,  the  challenge 
must  be  met  by  every  progressive  grower  if  this  crop 
is  to  be  placed  on  a  profitable  basis. 

The  present  work  has  no  apologies  to  offer.  No  one, 
more  than  the  writer,  realizes  the  shortcomings  of  this 
work.  However,  It  should  be  remembered  that  our 
knowledge  of  the  field  and  storage  conditions  of  the 
sweet  potato  are,  as  yet,  imperfectly  understood,  and 
the  literature  comparatively  meagre.  Recent  studies  by 
Hasselbring,  Harter,  Elliot,  Taubenhaus  and  others  have 


Introduction  ix 

added  considerably  to  our  knowledge  of  the  physiology 
and  pathology  of  the  sweet  potato.  However,  much 
more  remains  to  be  found  out.  Much  of  the  informa- 
tion here  contained  is  first  hand  and  represents  labora- 
tory research  and  field  experience  by  the  writer  for 
nearly  ten  years.  All  other  available  data  have  been  duly 
credited.    Constructive  criticism  is  earnestly  solicited. 

The  writer  is  indebted  to  Professors  A.  H.  Leidigh, 
W.  H.  Thomas  and  S.  C.  Hoyle,  of  the  Texas  A.  &  M. 
College  for  helpful  suggestions  in  reading  the  manu- 
script. Acknowledgments  are  also  due  to  many  sweet 
potato  growers  of  New  Jersey,  Delaware,  Maryland, 
Virginia,  Mississippi,  Georgia  and  Texas  for  informa- 
tion on  culture  contained  in  the  first  part  of  this  book. 
To  the  Agricultural  Experiment  Stations  of  Delaware 
and  Texas  the  author  is  especially  indebted  for  the  use 
of  all  the  original  photographs  taken  by  him  and  here 
presented.  All  other  borrowed  illustrations  were  prop- 
erly accredited.  Thanks  are  also  due  to  Mrs.  A.  H. 
Leidigh  for  reading  the  part  dealing  with  recipes;  to 
Miss  Stella  Stuart,  secretary  to  the  writer,  for  assist- 
ance in  preparing  the  index.  Last  but  not  least  to  my 
wife,  whose  moral  support  made  this  work  possible. 

J.  J.  Taubenhaus 
College  Station,  Texas 
March,  1923. 


CONTENTS 
Part  I 

CULTURE 

CHAPTER  PAGES 

I.  Origin  and  Production 3-14 

Origin  —  Distribution  —  Economic  impor- 
tance— Sweet  potato  production  in  foreign 
countries — Propagation — ^The  seed  (root) 
— Seed  selection  and  improvement — 
Number  of  sprouts  per  bushel  of  seed — 
Home-grown  seed — Storage-house  versus 
banked  seed — Seed  produced  from  vine 
cuttings. 

II.  Propagation  15-33 

The  propagating  or  hot-bed — Manure-heated- 
beds — Flue-heated  beds — Steam  or  hot 
water  beds — Cold  frame — Soil  for  the 
propagating  bed — Bedding  the  seed — Cov- 
ering the  hot-bed — Watering  the  hot-bed 
— Other  care  of  the  hot-bed — Hot-bed 
troubles — Seed  treatment  for  disease — 
Diseases  affecting  sprouts  in  the  hot-bed — 
Certified  seed — Inspection  service  in  Ar- 
kansas. 

III.  Drawing  Sprouts 34-62 

Drawing  sprouts — Number  of  draws  per  hot- 
bed— Buying  or  selling  sprouts — Cutting 
back  sprouts — Dipping  sprouts — Trans- 
planting— Ridge  versus  level  culture — 
Tools  for  transplanting — Machinery — Re- 
placing dead  hills — Soil  requirements — 
Preparation  of  the  soil — Rotation — Chemi- 
cal fertilizers — Stable  manure — Green  ma- 


xii  Contents 


CHAPTER  PAGES 

nure — Lime  or  hardwood  ashes — Effect  of 
fertilizers  on  vine  growth — Effect  of  fer- 
tilizers on  composition  of  sweet  potatoes — 
Cultivation — Irrigation — Effect  of  pinch- 
ing off  vines — Cost  of  production — Yield. 

IV.  Varieties   63-69 

Varieties — Groth's  Key  for  classifying  sweet 
potatoes — How  to  use  the  key. 

V.  Harvesting    70-78 

Harvesting — Implements  for  harvesting — 
Grading — United  States  grades  for  sweet 
potatoes — Hauling. 

VI.  Uses  of  the  Sweet  Potato 79-97 

Uses  of  the  sweet  potato — ^As  a  food — Cook- 
ing recipes — Sweet  potato  vines  for  forage 
— Sweet  potato  silage — Sweet  potato 
starch — Uses  for  sweet  potato  starch — 
Location  of  starch  factories. 


Part  II 
DISEASES 
VII.  Morphology  of  the  Healthy  Host. 


VIII.  Losses  from  Sweet  Potato  Diseases 105-123 

Losses  from  sweet  potato  diseases — Pox,  or 
pit  (soil  rot) — An  Actinomyces  associated 
with  pox — Powdery  slime  mold — White 
rust. 

IX.  Specific  Diseases 124-135 

Soft  rot — Ring  rot — Mucor  rot. 

X.  Specific  Diseases  (Continued) 136-146 

Giberella  rot — Dry  rot — Phyllosticta  leaf 
spot — Foot  rot — Black  rot — ^Java  black  rot. 


Contents  xiii 


CHAPTER 


PAGES 

XI.  Specific  Diseases  (Continued) H7-^5^ 

Septoria  leaf  spot— Trichoderma  rot— Bo- 
trytis  rot — Soil  stain  or  scurf — Alternaria 
rot — Vine  wilt,  or  stem  rot,  blue  stem 
Surface  rot— Other  Fusarium  rots. 

XII.  Specific  Diseases  (Continued) 159-166 

Epicocum  rot— Charcoal  rot— Cottony  rot — 
Texas  root  rot — Rhizoctonia  root  rot — 
Other  fungi — Non-parasitic  diseases — 
Hollow  heart— Net  necrosis— Mosaic. 

XIII.  Insects  and  Other  Pests 167-175 

Sweet  potato  weevil — Sweet  potato  and  yam 
quarantine — Flea  beetle — Tortoise  beetles 
— ^Termite  injury — Root  knot— Rat  and 
mice  injury. 


Part  III 


STORAGE  METHODS 

XIV.  Methods  of  Storing  Sweet  Potatoes 179-187 

Dehydration— Sweet  potato  flour— Canning 
sweet  potatoes — Storage  in  banks  and  in 
cellars. 

XV.  Physiological  Changes  During  Storage.  188-197 

XVI.  The  Curing  Period 198-220 

Temperature — Moisture — Methods  of  heat- 
ing sweet  potato  houses — Thermometers— 
Ventilation  —  Hygrometers  —  Care  after 
curing— Critical  periods  during  storage. 

XVII.  Storage  House  Consideration 221-227 

Preparing  the  house  for  storage— Filling  the 
house— Storing  in  bins  versus  containers. 


xiv  Contents 


CHAPTER  PAGES 

XVIII.  Construction     of     Commercial     Curing 

Houses  228-233 

Type  of  house — Foundation — Walls — Aisle 
space — Ventilators — Cupola — Bins — Load- 
ing platform. 

XIX.  Estimate      Requirements      of      Storage 

Houses  234-263 

The  small  house — Bill  of  materials  for  a 
500-bushel  house — Bill  of  materials  for  a 
2500-bushel  house — The  5000-bushel  wnit 
house — The  medium-sized  house — Large 
hoMses — Patent  houses — The  Bradley  sys- 
tem— The  Delaware  system — The  Wells 
system — The  Nordin  system — The  Win- 
field  system — The  Woods  system — Im- 
provement of  faulty  potato  houses — Man- 
agement. 

XX.  Marketing    264-273 

Containers — Care  in  shipping — Shipping 
sweet  potatoes  abroad — Sweet  potato  score 
card — Sweet  Potato  Association  of 
America. 

Bibliography   274-281 

Index  283-286 


ILLUSTRATIONS 

FIGURE  FACING  PAGE 

1.  Seed  Selection 8 

2.  Field  Operations   i5 

3.  Pulling  Sprouts 22 

4.  Dipping  Sweet  Potato  Seed , 24 

5.  Sweet  Potato  Starch  Factory 94 

6.  Morphology  of  Healthy  Host 103 

7.  Sweet  Potato  Pox 109 

8.  Slime  Mold   119 

9.  Soft  Rot 126 

10.  Soft  Rot 128 

11.  Ring  Rot I33 

12.  Dry  Rot I37 

13.  Foot  Rot 140 

14.  Black  Rot I43 

15.  Java  Black  Rot I45 

16.  Soil  Stain 152 

17.  Trichoderm'a  Rot  iS4 

18.  Fusarium  Wilt  i57 

19.  Various  Diseases  160 

20.  Various  Diseases I74 

21.  Storage  Methods 180 

22.  Unit  House 243 

23.  Method  of  Loading  and  Filling  the  House 249 

24.  Brick  Houses  254 

25.  Commercial  Houses  258 

26.  Frame  Structures  260 

27.  Patent  Houses 261 

28.  Patent  Houses 263 

29.  Marketing   ,,,,.,,,,, 268 


THE 
CULTURE  AND  DISEASES 
OF  THE  SWEET  POTATO 


PARTI 
CULTURE 


CHAPTER  I 

origin  and  production 

Origin 

During  the  last  four  hundred  years,  the  sweet  potato 
has  fully  established  itself  in  the  tropics  and  sub-tropics. 
Nevertheless,  its  true  home  of  origin  is  still  problemati- 
cal. Humboldt,  Meyer,  and  Boissier  maintain  that  the 
sweet  potato  is  of  American  origin,  while  Boyer,  Choisey 
and  others  contend  that  its  original  home  is  Asia.  The 
arguments  in  favor  of  its  American  origin  are  based  on 
the  contention  that  the  fifteen  known  species  of  the 
genus  Batatas  are  found  in  America,  while  only  four  of 
these  occur  in  Asia.  Moreover,  Marcgraff  described  it 
from  Brazil  as  Jetica.  The  name  "batata"  originated 
from  a  misinterpretation  of  "potato"  which  is  really  a 
Mexican  word.  When  Columbus  appeared  before 
Queen  Isabella  he  presented  her,  among  his  many  pres- 
ents, with  a  sweet  potato  which  he  found  growing  in 
America. 

The  sweet  potato  was  not  known  among  the  Greeks, 
Romans,  Hebrews,  Arabs,  or  Egyptians.  However,  its 
supposed  Asiatic  origin  is  based  on  the  contention  that 
the  Chinese  Encyclopedia  of  Agriculture  describes  some 
varieties  of  sweet  potatoes.  On  the  whole,  however,  it 
is  generally  conceded  that  America  was  the  original 
home  of  the  sweet  potato. 

3 


The  Sweet  Potato 


Distribution 

The  sweet  potato  is  best  adapted  to  the  Southern 
States,  yet  it  is  grown  as  far  north  as  New  Jersey  and 
as  far  west  as  central  CaUfornia.  For  successful  com- 
mercial production  the  crop  requires  a  growing  season 
of  at  least  four  and  a  half  months  from  field  planting 
to  fall  frost,  fairly  warm  nights,  and  a  moderate 
amount  of  rainfall.  It  is  also  grown  extensively  in 
Mexico,  Central  and  South  America,  Argentine,  and 
Chile.  In  Africa,  sweet  potatoes  are  grown  largely  by 
the  natives  of  all  the  European  colonies,  and  by  those  of 
the  interior.  The  crop  is  also  well  known  in  Mediter- 
ranean Europe  and  in  Syria  and  Palestine.  In  Persia, 
Hindustan,  India,  China,  Japan,  and  the  Malay  Archi- 
pelago it  forms  a  staple  food  product.  Sweet  potatoes 
are  also  grown  extensively  in  Australia  and  New  Zea- 
land. 

Economic  Importance 

In  the  United  States  the  sweet  potato  is  second  in  im- 
portance only  to  the  Irish  potato  as  a  truck  crop.  Ac- 
cording to  Miller  (69*)  the  area  in  191 7  devoted  to 
sweet  potatoes  in  the  United  States  was  estimated  to  be 
953,000  acres,  the  production  87,141,000  bushels,  and 
the  value  $96,121,000.  The  farm  value  of  sweet  pota- 
toes, which  has  doubled  in  the  last  ten  years,  has  in- 
creased more  rapidly  than  the  acreage  and  production. 
This  is  no  doubt  due  to  improved  methods  of  storing 
and  marketing  the  crop.  In  the  Southern  States,  the 
sweet  potato  is  considered  one  of  the  principal  food 
crops,  and  in  recent  years  the  acreage  has  been  rapidly 

*  All  numbers  in  parenthesis  refer  to  Bibliography  at  the  close  of 
this  work. 


Origin  and  Production 


increased.  Texas,  for  instance,  hardly  as  yet  produces 
enough  to  supply  its  own  home  markets,  importing 
largely  from  Louisiana  and  Arkansas  (Statistical  fig- 
ures not  available).  Table  i  shows  the  acreage,  yield 
per  acre,  and  value  of  the  sweet  potato  for  1912  and 
19 1 3  in  the  United  States. 

Table  i 

Acreage,  Production,  and  Value  of  Sweet  Potatoes, 

JQ12  and  191 J  * 


States 

Acreage 

(000 
Omitted) 

Yield  per 

Acre 

in 

Bushels 

Total  Pro. 
duction 

(000 
Omitted) 

Price  per 

Bushel 
December  I 

to 
Producers 

Value  Based 
on  Prices 
December  i 

to 
Producers 

{000 
Omitted) 

1913 

1912 

1913 

1912 

1913 

1912 

1913 

191a 

1913 

1912 

New  Jersey 

Pennsylvania.... 

Delaware 

Maryland 

Virginia 

West  Virginia... 
North  Carolina.. 
South  Carolina .  . 
Georgia 

Acres 

23 

I 

S 

8 

33 

2 
80 
SO 
83 
21 

I 
I 
8 
2 
6 

S 

9 
20 
70 
SS 

60 
50 

6 
20 

6 

Acres 

23 

I 

5 

8 

33 

li 

81 
21 

I 
I 

8 
2 
6 

S 

9 
20 
62 
52 

Sf 
36 

6 

Bu. 
138 
110 
135 

108 

91 
100 

I? 

no 

90 
78 
70 
80 
56 

50 

75 
80 

95 
98 

85 
80 
64 
90 
170 

Bu. 
120 
120 
120 

125 

90 

115 
90 

los 
90 
112 

118 
116 
98 

18^ 

99 
90 
90 
100 
97 

84 
75 

u 

156 

Bu. 

3174 
no 
675 

1128 

3564 

182 
8000 
4600 
7221 
2310 

?8 
S6o 
160 
336 

250 

67s 
1600 

6650 

5390 

Sioo 

4000 
1800 

1020 

Bu. 

2760 
120 
600 

1000 

2970 

230 
6750 
S040 
7290 
2352 

118 
116 
784 
180 
528 

495 
810 
1800 
6200 
5044 

4704 
2700 

368 
1584 

936 

Cts. 
78 

ro 
60 
70 

100 
61 

u 
75 

106 
103 
106 
150 
105 

no 

ti 
tl 

70 
95 

104 
80 

100 

Cts. 
84 

11 
63 
75 

r. 

68 
66 
73 

87 
89 

95 

"4 

72 
71 
62 

65 
104 
109 
90 
94 

Dolls. 

2476 

99 

40s 

677 

2495 

182 
4880 
3450 
4910 
1732 

11 
594 
240 
353 

275 

634 

1280 

4456 

3342 

3570 
3800 
399 
1440 
1020 

Dolh. 
2318 

9? 
408 
630 
2228 

207 
418s 
3427 
48n 
1717 

103 
103 
745 
194 
503 

688 
1296 
4403 
3127 

3058 
2808 

Ohio 

Missouri 

Kentucky 

Tennessee 

Alabama 

Mississippi 

Louisiana 

Texas 

Oklahoma 

Arkansas 

California 

401 
1426 
880 

United  States. . 

62s 

583 

92.5 

92.2 

S9IS7 

55479 

72.6 

72.6 

42884 

40264 

Table  i  is  taken  from  the  U.  S.  Dept.  Agr.,  Farm.  Bui.  570,  1913. 


The  Sweet  Potato 


Sweet  Potato  Production  in  Foreign  Countries 

Although  the  sweet  potato  is  so  extensively  grown, 
data  of  production  for  other  countries  are  very  meager. 
According  to  Leon  M.  Estabrook,  Chief  of  the  Bureau 
of  Crop  Estimates,  United  States  Department  of  Ag- 
riculture, no  country  of  Europe,  excepting  Spain,  pub- 
lished statistics  on  the  production  of  sweet  potatoes. 
They  are  practically  unknown  in  the  United  Kingdom. 
In  Spain  the  area  in  19 lo  was  4584  acres,  with  a  pro- 
duction of  48,600  tons,  2000  pounds  to  the  ton. 

In  the  1907-8  Census  of  Argentina  the  area  under 
sweet  potatoes  in  that  year  is  given  as  30,107  acres. 
Statistics  of  agricultural  production  in  all  countries  of 
South  America,  excepting  Argentina,  Chile,  Uruguay, 
are  practically  non-existent.  No  statistics  are  known  re- 
specting sweet  potato  production  in  Africa. 

Statistics  as  given  by  Daugherty  (14)  for  Japan  and 
Formosa  show  that  in  the  former  country  for  191 1,  the 
area  in  sweet  potatoes  was  720,121  acres  with  a  produc- 
tion of  4,156,052  tons  (2000  pounds  to  the  ton).  In 
Formosa  for  19 11,  the  area  in  sweet  potatoes  was 
265,156  acres,  with  a  production  of  747,305  tons. 


Propagation 

Sweet  potatoes  are  propagated  by  means  of  seed 
sprouts  and  vine  cuttings.  Botanically  speaking,  the 
sweet  potato  is  not  a  tuber  like  the  Irish  potato,  which  is 
considered  an  underground  stem.  It  is,  however,  con- 
sidered a  root  having  dormant  shoots  near  the  lenticels. 
The  sweet  potato  should  not,  therefore,  be  spoken  of  as 
a  tuber  as  is  so  loosely  done  in  the  literature  of  this  crop. 
It  is  seldom  reproduced  from  seed  obtained  from  fer- 


Origin  and  Production  7 

tilization  of  its  blossoms.*  Likewise  it  seldom  if  ever 
produces  blossoms  except  in  the  tropical  countries,  in 
which  case  the  flower  resembles  that  of  the  morning 
glory.  Gonzalo  (25)  states  that  in  the  Philippines,  the 
varieties,  Samar  Big  Yellow,  Canegro,  Sinomporado, 
and  Beriberi  flower  profusely  and  produce  true  seed.  In 
the  United  States  the  sweet  potato  is  reproduced  by 
means  of  roots  which  are  generally  spoken  of  as  seed. 
Price  (80)  states  that  propagation  may  be  effected  by 
means  of  pieces  of  the  root,  in  the  same  manner  as  the 
Irish  potato  is  propagated.  This  method  could  only  be 
used  in  warm  climates  where  cold,  damp  weather  is  not 
likely  to  prevail  in  the  spring.  With  this  method,  the 
root  is  sliced  in  two  or  more  pieces  and  planted  in  the 
rows  in  the  field  about  the  same  as  are  Irish  potatoes. 
However,  on  a  large  scale,  this  method  is  impractical 
and  expensive.  It  will  require  planting  as  many  bushels 
per  acre  as  for  Irish  potatoes.  The  standard  method  is 
to  plant  the  roots  In  hot-beds,  and  as  soon  as  the  sprouts 
are  large  enough  they  are  pulled  and  planted  in  the  open 
field.  The  number  of  bushels  required  to  supply  the 
necessary  sprouts  per  acre  is  indicated  on  p.  9. 

The  Seed  (root) 

It  is  poor  practice  indeed  to  sell  out  the  choicest  grade 
of  sweet  potatoes  and  to  leave  for  seed  "shoe  strings," 
deformed  roots,  jumbos  and  culls.  This  practice,  if  al- 
lowed to  prevail,  may  have  a  tendency  to  develop  un- 
desirable run-out  strains.  Johnson  and  Rosa  (57)  state 
that  experiments  at  the  Virginia  Truck  Station  have 
generally  shown  no  disadvantage  in  the  use  of  small  po- 

*  The  term  seed  potatoes  as  it  is  used  in  this  work  refers  to  the 
edible  root  as  it  is  also  used  for  planting  in  the  hot-bed. 


8  The  Sweet  Potato 

tatoes,  provided  they  come  from  healthy  hills,  This, 
however,  needs  further  verification.  The  author  (103)' 
has  shown  that  the  use  of  the  medium-sized  roots  when 
treated  with  corrosive  sublimate  will  yield  stocky 
sprouts.  It  is  also  claimed  by  many  growers  that  such 
seed  produce  more  vigorous  plants.  The  smaller  seed 
produce  a  larger  number  of  sprouts,  and  this  is  why  they 
are  especially  preferred  by  growers  who  sell  plants.  It 
is  doubtful,  however,  if  such  sprouts  are  of  a  high 
quality.  The  use  of  jumbos  for  seed  is  not  advocated 
unless  they  are  cut  up  and  treated  with  bichloride  (see 
p.  24).  Jumbo  seed  generally  yield  less  sprouts  in  pro- 
portion to  their  weight,  hence  there  is  waste  in  hotbed 
space. 

Seed  Selection  and  Improvement 

The  only  practical  basis  of  selection  is  the  hill  unit 
(Fig.  I,  a).  The  mistake  is  often  made  of  selecting 
seed  from  the  bins  at  the  end  of  the  storage  season.  In 
this  case,  where  the  individual  root  is  the  unit  of  selec- 
tion, the  largest  potato  may  often  come  from  a  diseased 
hill  or  from  a  hill  of  low  production,  which  we  would 
not  want  to  propagate.  In  selecting  seed  we  should  dis- 
card all  hills  which  show  disease  of  any  kind.  A  search 
should  be  made  for  the  highest  yielding  hills,  and  the 
potatoes  from  these  should  be  stored  and  planted  sep- 
arately. Hills  with  less  than  five  average,  good,  healthy, 
marketable  potatoes  should  be  discarded  as  unfit  for 
seed.  Hills  producing  numerous  small  and  undersized 
roots  should  not  be  used.  Selections  by  the  average 
grower  are  generally  made  by  going  over  the  field  dur- 
ing harvesting  time  and  picking  out  the  best  producing 
hills.  A  more  reliable  method  is  as  follows:  The  best 
looking  field  is  picked,  keeping  in  mind  especially  free- 


I'iG.  I.     Seed  Selection. 

a.  Ideal    swpet    potato  hill    suited    for    seed    punwses.     b.    Showing 

method   of   hill  selection  in  the  field,     c.  Sweet   potato  digger  (after 
W.  H.  Wicks'). 


Origin  and  Production  9 

dom  from  disease  on  the  foliage  and  vines.  The  hills 
are  then  plowed  out,  two  or  three  rows  at  a  time,  using 
the  plow  (Fig.  i,  c)  described  on  p.  73.  Instructions 
are  given  to  the  picker  to  lift  out  each  hill  from  the 
soil,  without  detaching  any  of  the  roots  from  the  mother 
stem.  This  may  easily  be  done  by  taking  hold  of  the 
base  of  the  plant  and  firmly  lifting  it  out  of  the  loosened 
soil.  These  hills  are  then  carefully  placed  on  a  pile  in 
the  row,  all  the  roots  being  put  on  the  same  side.  Two 
or  more  of  the  most  intelligent  and  reliable  helpers 
should  now  sit  down  near  the  pile,  and  examine  each 
hill,  individually  (Fig.  i,  b),  discarding  the  undesirable 
and  saving  the  best.  These  are  put  away  and  stored  in 
separate  containers,  and  are  carefully  reselected  in  the 
spring  to  determine  their  freedom  from  rots  before 
planting.  It  is  suggested  that  a  special  "seed  plat"  area 
be  carried  by  storage  men,  marketing  associations  and 
dealers  in  sprouts.  Sprouts  from  seed  of  the  best  se- 
lected hills  should  be  planted  in  separate  rows.  By  this 
means,  improvement  may  be  made  in  shape  and  yield  of 
the  selected  strains. 


Number  of  Sprouts  per  Bushel  of  Seed 

It  is  estimated  that  a  bushel  of  medium-sized  potatoes 
will  produce  1500  to  2500  sprouts  when  three  drawings 
are  made.  With  rows  four  feet  apart,  and  the  plants 
eighteen  inches  in  the  row  7000  sprouts  to  the  acre  will 
be  required.  If  the  rows  are  closer  than  four  feet, 
8  to  12,000  sprouts  may  be  required. 

Sprout  or  Draw.  By  sprout  is  here  meant  the  plants 
from  a  sprouted  mother  potato  in  the  hot-bed.  These 
sprouts  are  detached  or  drawn,  and  planted  in  the  field. 
Growers  frequently  make  one  to  three  pullings  from 


10  The  Sweet  Potato 

the  same  hot-bed.  In  many  of  the  Southern  States  the 
term  "slip"  is  used  instead  of  sprout.  The  term  "sUp," 
however,  may  be  misleading  to  some  of  the  Northern 
growers,  who  infer  it  to  mean  vine  cuttings.  It  seems 
desirable  that  the  term  slip  should  in  this  case  be  dis- 
carded and  the  word  sprout  adhered  to. 

Home-Grown  Seed 

For  many  reasons  home-grown  seed  are  to  be  pre- 
ferred. They  are  especially  desirable  when  the  possi- 
bility of  disease  is  considered.  Without  any  pure  seed 
laws  or  a  system  of  inspection  in  many  states  we  seldom 
if  ever  know  whether  or  not  the  imported  seed  comes 
from  disease-free  land.  There  seems  no  doubt  but  that 
most  of  the  sweet  potato  diseases  were  spread  about 
promiscuously  with  imported  seed.  The  grower  in  pro- 
ducing home-grown  seed  and  sprouts  is  able  to  make  his 
own  selections,  and  to  avoid  infected  fields.  This  fact 
is  fully  agreed  upon  by  the  most  progressive  growers. 
What  applies  to  imported  seed  also  holds  true  with  the 
sprouts.  It  has  been  shown  by  Garcia  (24)  that  im- 
ported sprouts  die  out  much  more  quickly  from  disease 
than  home-grown  sprouts.  This  is  very  evident.  Sprouts 
are  nothing  more  than  tender-rooted  cuttings.  If  they 
are  not  immediately  transplanted  after  "drawing,"  they 
will  wilt,  weaken,  and  become  susceptible  to  all  sorts  of 
diseases.  Frequently,  imported  sprouts  are  delayed 
three  to  five  days  from  the  time  they  were  "drawn"  to 
planting.  When  a  large  percentage  of  these  sprouts  die, 
we  not  only  introduce  disease  in  the  soil,  but  the  uneven 
broken  stand  results  in  reduced  yields.  Stuckey  (93) 
found  that  home-grown  plants  produced  heavier  yields 
than  shipped  plants.    This  is  shown  in  Tables  2  and  3. 


Origin  and  Production 


II 


Table  2 
Yield  of  Home-Grown  versus  Purchased  Plants 


Variety 

Pounds  Potatoes  from 
Home-grown  Plants 

Pounds  Potatoes  from 
Purchased  Plants 

Triumph 

1055 
853 
771 
630 

725 
555 
602 

Golden  Beauty 

Nancy  HaU 

Big  Stem  Jersey 

533 

Table  3 
Yield  of  Home-Grown  versus  Purchased  Seed 


Variety 


Pounds 
Marketable 
Potatoes 

Pounds 

Small 

Potatoes 

773 
406 

80 
149 

390 

49 

455 

29 

Total 
Pounds 
Potatoes 


1912 

Golden  Beauty,  home-grown . 
Golden  Beauty,  ordered , 


1913 

Golden  Beauty,  home-grown. , . 

Golden  Beauty,  with  one  year'i 

acclimatization 


853 
555 


439 

484 


The  difference  in  yield  in  favor  of  the  home-grown 
sprouts  may  be  due  either  to  the  set-back  the  plants  re- 
ceived during  shipping,  or  to  a  lack  of  acclimatization, 
or  to  disease. 


Storage-House  Versus  Banked  Seed 

There  are  growers  in  the  Southern  States  who  hesi- 
tate to  use  the  so-called  kiln-dried  or  storage-house  seed, 
fearing  that  such  seed  germinate  poorly.     This,   of 


12  The  Sweet  Potato 

course,  has  never  proved  true,  since  most  growers  store 
their  sweet  potatoes  in  kiln-dried  warehouses  only  and 
no  difficulty  is  ever  experienced  in  the  germination  on 
that  account.  The  prejudice  against  kiln-dried  seed 
may  perhaps  be  traced  back  to  a  few  individual  mishaps 
where  seed  have  failed  to  sprout,  not  because  of  being 
kiln-dried,  but  because  of  soft  rot  in  the  hot-bed  and 
previous  rough  handling  and  failure  to  disinfect  against 
disease.  It  must  be  conceded  that  banked  seed  gen- 
erally sprout  earlier  than  kiln-dried  seed,  and  for  this 
reason  are  preferred  by  growers  who  sell  plants.  Such 
sprouts,  however,  are  no  better  than  those  from  kiln- 
dried  seed.  It  is  true  the  latter  sprout  more  slowly  but 
they  produce  stockier,  firmer  and  healthier  plants. 

Seed  Produced  from  Vine  Cuttings 

From  the  viewpoint  of  disease  control  seeds  produced 
from  vine  cuttings  are  to  be  preferred.  They  may  be 
easily  produced  in  nearly  all  the  Southern  States,  from 
Virginia  to  the  coast.  The  seeds  (roots)  from  vine  cut- 
tings are  usually  small-sized,  but  smooth,  well-shaped, 
free  from  disease,  and  are  only  used  the  following  year. 
The  method  of  production  is  as  follows :  In  the  fall,  dur- 
ing digging  time,  the  roots  from  the  best,  selected,  and 
healthiest  hills  should  be  stored  away  separately  in  con- 
tainers and  properly  cared  for.  The  following  spring 
these  seed  are  reselected  for  freedom  from  disease  and 
the  roots  disinfected  in  bichloride  of  mercury  (see 
p.  24).  After  the  treatment  they  are  planted  in  the  hot- 
bed in  the  usual  way.  The  sprouts  from  these  are  pulled 
and  planted  early  in  a  field  known  to  be  free  of  disease, 
or  if  possible  in  new  land.  As  soon  as  vines  are  pro- 
duced, cuttings  8  inches  to  12  inches  long  are  made,  and 


Origin  and  Production  13 

these  planted  as  though  they  were  rooted  sprouts  In  a 
well-prepared  soil.  The  roots  which  grow  from  these 
cuttings  at  the  end  of  the  season  will  be  the  seed  from 
vine  cuttings.  These  are  to  be  stored  away  separately 
and  the  following  spring  planted  in  the  hot-bed  for  the 
purpose  of  producing  the  sprouts  for  the  main  crop. 
Before  planting  out  the  vine  cuttings,  one  should  pinch 
off  all  the  leaves  except  those  at  the  tip.  This  will  pre- 
serve the  food  of  the  cutting  before  it  takes  root.  The 
tip  of  the  vine  is  often  too  tender ;  hence  it  should  not  be 
used  as  a  cutting.  To  get  the  best  results,  the  cuttings 
should  be  ready  to  be  planted  in  the  field  as  soon  as 
danger  from  frost  is  over.  The  cuttings  are  planted  4 
to  5  inches  apart  in  the  row,  the  rows  being  about  32 
inches  apart.  They  are  set  either  by  hand  or  with  the 
machine  planter,  and  are  inserted  4  to  6  inches  in  the 
ground  and  set  firmly. 

Some  growers  believe  that  where  slip  seed  are  pro- 
duced, no  more  extra  precaution  is  necessary  to  avoid 
diseases.  This,  however,  is  not  the  case.  Slip  seed  are 
as  a  rule  free  from  disease,  because  the  vine  cuttings 
which  originate  them  are  supposed  to  be  healthy.  How- 
ever, if  the  cuttings  are  taken  from  diseased  hills  or 
planted  in  sick  soil  the  resulting  roots  will  not  be  free 
from  disease. 

Some  growers  in  New  Jersey,  Delaware  and  Virginia 
claim  larger  yields  from  seed  of  vine  cuttings.  Others 
on  the  other  hand  prefer  the  sprouts  to  seed  from  vine 
cuttings  believing  tfiat  the  latter  method  will  eventually 
cause  the  strain  to  run  out.  This,  however,  is  a  disputed 
question  with  the  balance  in  favor  of  seed  from  vine 
cuttings.  The  practicability  of  this  method  will  largely 
be  determined  by  the  length  of  the  growing  season,  and 
by  the  summer  rainfall.    Wherever  possible,  seed  from 


14  The  Sweet  Potato 

vine  cuttings  should  be  produced  at  least  once  every 
second  or  third  year.  This  practice  will  tend  to  elim- 
mate  soil  stain  (Monilochaetes  infuscans) ;  vine  wilt 
(Fusariimi  hyperoxysporum  and  F.  batatatis) ;  and 
black  rot  {Ceratostomella  fimbriata). 


Fig.  2.     Field  Oi>i:kati()NS. 

fl.  Transplantinj^  machine  for  sweet  potato  sprouts,     h.  Hand  transplanter. 
c.  Flue-heated  hotbed  .showing  below,  (ire  box,  and  above,  the  hotbed. 


CHAPTER  II 
propagation 

The  Propagating  or  Hot-bed 

By  propagating  bed  is  here  meant  any  bed  (irrespec- 
tive of  the  method  of  heat  used)  where  sweet  potato 
seed  (roots)  are  sprouted,  and  the  sprouts  used  for  field 
planting.  The  propagating  bed  requires  as  much  care 
as  the  seed.  Failure  to  recognize  this  makes  it  a  breed- 
ing place  for  disease. 

Location  of  Bed.  The  propagating  bed  should  never 
be  located  near  the  sweet  potato  storage  house  (Fig.2,  c). 
The  rotted  potatoes  which  are  frequently  dumped  out 
carelessly  around  the  storage  house  will  in  due  time  be 
broken  up  and  crushed  by  workmen  and  farm  animals, 
and  finally  find  their  way  into  the  hot-bed,  infecting  it 
with  black  rot  and  many  other  diseases.  The  ideal  loca- 
tion is  high,  well-drained  land,  with  unobstructed  sun- 
light, protected  from  cold  and  preferably  near  the  dwell- 
ing house.  The  south  or  southeast  side  of  a  thick  wood 
will  also  offer  a  desirable  place.  In  the  absence  of  this 
the  beds  may  be  enclosed  with  a  tight  board  fence,  and 
in  some  cases  a  good  windbreak  on  the  exposed  and 
windy  side  will  suffice. 

When  early  sprouts  are  desired,  some  form  of  heat  is 
necessary.    This  may  be  supplied  in  various  ways. 
15 


i6  The  Sweet  Potato 

Manure-Heated  Beds 

Heat  can  De  most  cheaply  furnished  to  the  sprouting 
roots  in  the  beds  by  means  of  manure.  The  general 
practice  is  to  make  an  excavation  12  to  18  inches  deep, 
under  the  frame  which  is  about  6  feet  wide,  and  as  long 
as  desired.  The  framework  consists  of  12-inch  boards 
on  the  north  or  west  side,  and  6-to-8-inch  boards  on  the 
south  or  east  side,  both  ends  being  boxed  up.  The  sides 
of  the  frame  are  held  in  place  by  stakes,  or  nails,  or  by 
dirt  piled  up  on  either  side.  The  latter  helps  to  keep 
out  the  cold.  A  more  permanent  hot-bed  may  be  made 
by  using  concrete  instead  of  boards  for  the  walls. 

The  manure,  preferably  from  the  stable,  should  be 
turned  once  or  twice  to  make  it  uniform  in  texture.  It 
is  then  placed  in  the  excavation  to  about  8  to  12  inches 
depth  and  well  trampled  down.  If  the  manure  is  too 
dry,  water  should  be  added  to  it.  When  heating  starts, 
clean  sand  is  spread  evenly  over  the  manure  to  a  depth 
of  3  to  4  inches,  and  planting  is  not  safe  until  the  tem- 
perature drops  to  80  or  85  degrees  F.  After  the  hot-bed 
season  is  over  the  manure  may  be  taken  out  from  the  bed 
and  spread  on  the  field  or  in  the  garden. 

Manure  is  a  cheap  fuel  and  is  abundant  on  the  aver- 
age farm.  On  large  bed  areas,  and  where  manure  is 
scarce,  its  price  becomes  too  high  to  justify  its  use. 
Moreover,  manure  is  apt  to  carry  disease. 

Flue-Heated  Beds 

Where  manure  is  scarce,  or  too  expensive,  and  where 
large  quantities  of  sprouts  are  produced,  flue-heated 
beds  (Fig.  2,  c)  become  very  desirable.  The  best  way  to 
construct  these  is  described  by  Price  (81).  The  walls 
are  constructed  of  concrete   or   boards,    treated   with 


Propagation  17 

creosote  to  preserve  them  longer.  The  frame  is  located 
on  a  well-drained  place,  sloping  to  the  south  or  south- 
east, and  protected  from  north  or  northwest  winds. 

The  fire  box  is  constructed  of  brick,  i8  inches  wide 
(inside  measurements),  20  inches  high,  and  4  feet,  8 
inches  long.  The  terra  cotta  flue  pipe,  leading  under  the 
bed,  is  8  inches  in  diameter,  extending  the  entire  length 
of  the  frame  into  the  chimney  at  the  other  end.  Some 
growers  extend  the  flue  pipe  only  two-thirds  of  the 
length  of  the  bed.  This,  however,  is  dangerous  as  the 
escaping  sparks  often  cause  the  bed  to  catch  fire  when 
the  bottom  is  constructed  of  logs.  The  first  2  or  3  joints 
of  the  flue  should  be  covered  with  brick,  as  a  blaze  from 
the  fire  box  might  cause  it  to  become  too  hot  and  en- 
danger the  floor.  The  chimney  may  be  made  of  brick  or 
of  4-inch  boards,  nailed  in  box  fashion.  To  draw  better, 
the  bottom  opening  of  the  chimney  under  the  floor 
should  be  larger  than  the  flue.  The  wooden  floor  is  built 
4  to  6  inches  above  the  flue,  to  give  a  better  dis- 
tribution of  heat  and  to  prevent  it  from  catching  fire. 
The  floor  should  have  a  slope  of  12  inches  in  90  feet 
or  I  inch  to  each  yYz  feet.  The  flue  under  the  floor 
should  have  the  same  slope  as  the  floor;  that  is,  the 
soil  at  the  furnace  end  should  be  18  inches  deep  and 
at  the  chimney  end  6  inches  deep.  The  soil  on  top  of 
the  frame  should  be  level.  The  floor  above  the  flue  may 
be  of  logs  or  of  any  kind  of  rough  lumber  treated  in 
creasote.  The  fuel  for  flue  beds  may  consist  of  any 
kind  of  logs  cut  to  fit  in  the  fire  box.  It  takes  about 
seven  loads  of  wood  during  the  season  to  heat  a  10X50 
ft.  flue  bed.  The  advantage  in  this  system  is  its  cheap- 
ness of  construction.  The  disadvantage  is  that  the  end 
nearest  to  the  chimney  is  often  coldest,  and  it  takes  the 
seed  longer  to  sprout. 


i8  The  Sweet  Potato 


Steam  or  Hot  Water  Beds 

Where  a  steam  or  hot  water  boiler  is  used  in  connec- 
tion with  a  greenhouse,  it  may  be  conveniently  employed 
for  the  sweet  potato  beds.  On  a  large  scale  it  will  pay 
to  install  a  steam  or  hot  water  system,  even  though  it  is 
used  for  no  other  purpose  than  sweet  potato  hot-beds. 
With  this  method  the  heat  is  better  regulated,  and  main- 
tained at  a  more  even  temperature. 

With  steam  or  hot  water,  the  best  results  are  obtained 
when  the  pipes  are  placed  on  the  bottom  of  the  hot-bed 
pit.  The  soil  in  this  case  is  put  on  tile  or  on  a  board 
floor  which  rests  on  pipe  or  wood  supports,  a  space  of 
3  to  4  inches  being  left  between  the  floor  and  the  bottom 
of  the  pit.  According  to  Miller  (69)  the  number  and 
size  of  heating  pipes  required  will  depend  on  the  rapid- 
ity of  the  circulation,  on  the  pressure  of  the  steam,  or  the 
temperature  of  the  water.  With  hot  water,  and  with 
beds  not  over  50  feet  long,  four  1 3^ -inch  pipes  will 
suffice.  For  longer  beds,  2-inch  pipes  should  be  used. 
Two  of  the  pipes  will  serve  as  flow,  and  two  as  returns. 
The  place  where  the  pipes  enter  the  bed  should  be  the 
highest  in  the  system,  and  where  the  pipes  leave  the 
bed,  the  lowest.  The  pipes  should  have  a  uniform 
grade,  and  be  evenly  spaced.  The  flow  pipes  should 
be  laid  about  a  foot  from  each  outside  wall,  and  the  re- 
turns in  the  middle.  With  steam  the  arrangement  is  the 
same,  except  that  smaller  pipes  are  used.  With  steam  at 
10  pounds  pressure,  and  for  a  50- foot  bed,  i-inch  pipes 
are  sufficient.  For  beds  up  to  100  feet  long,  134 -inch 
pipes  are  necessary.  The  boiler  house  may  be  8  feet 
wide,  10  feet  long,  and  6^2  feet  deep  below  ground 
level.    With  a  hot-water  system,  the  heat  is  more  evenly 


Propagation  19 

and  regularly  distributed  and  is  more  easily  managed 
than  steam. 

Cold  Frame 

In  many  of  the  Southern  States,  no  heat  whatever  is 
used  in  sprouting  the  seed.  In  this  case,  a  pit  is  dug 
10x50  feet  and  about  6  inches  deep,  bordered  by  a  frame- 
work of  boards,  or  the  sides  are  banked  up  with  soil. 
With  this  method,  however,  the  sprouts  are  late.  Pro- 
tection from  frost  or  cold  is  secured  by  means  of  a 
canvas. 

Soil  for  the  Propagatij>tg  Bed 

Experiments  by  Price  (8i)  and  by  others  have  defi- 
nitely proved  that  sweet  potatoes  bedded  in  sand  pro- 
duce plants  with  better  rootlets  than  when  bedded  in 
clay  or  loamy  soil.  Neither  fertilizer  nor  compost  is 
necessary  as  plant  food  for  bedded  potatoes,  as  the  sweet 
potato  sprouts  draw  most  of  their  nourishment  from  the 
mother  potato.  Moreover,  from  a  hygienic  point  of 
view  the  use  of  clean  sand  for  bedding  will  keep  out 
many  diseases  which  otherwise  may  be  brought  in  with 
the  manure. 

Bedding  the  Seed 

The  time  for  bedding  the  seed  for  the  production  of 
sweet  potato  sprouts  varies.  As  a  rule,  sweet  potatoes 
are  bedded  about  six  weeks  before  the  date  on  which  it 
is  expected  to  transplant  the  first  lot  of  sprouts  in  the 
field.  In  most  northern  sections,  sweet  potatoes  are 
bedded  about  a  month  before  danger  of  frost  is  over. 

The  seed  should  never  be  bedded  until  the  tempera- 
ture of  the  hot-bed  soil  remains  stationary  at  78  to  80 
degrees  F.  It  is  always  necessary  to  have  one  or  more 
thermometers  in  the  hot-bed.    The  temperature  should 


20  The  Sweet  Potato 

be  read  every  day.  The  air  temperature  beneath  the 
sash  or  cover  should  be  maintained  at  not  less  than  60 
degrees,  or  above  80  degrees  F.  During  bright  days 
plenty  of  ventilation  should  be  given,  by  opening  the 
sash  or  uncovering  the  bed. 

The  potatoes  are  planted  by  hand  on  the  hot-bed  soil, 
a  space  of  Yz  inch  being  left  between  each  potato. 
It  is  best  to  bed  all  the  seed  of  the  same  size  together. 
In  this  way  they  may  all  be  covered  to  the  same  depth. 
The  very  large  ones  may  be  cut  in  halves,  lengthwise  and 
laid  in  the  bed  flat  side  down.  In  order  to  hold  the  roots 
firmly  and  to  prevent  their  disturbance  or  uprootings 
later  when  the  sprouts  are  pulled,  it  is  usually  customary 
with  growers  in  Delaware  and  Maryland  to  cover  the 
seed  with  the  sand  or  with  a  thin  layer  of  pine  needles. 
This  is  done  in  order  to  hold  the  mother  roots  when  the 
sprouts  are  drawn.  A  better  method,  however,  is  that 
recommended  by  Price  (81)  and  consists  in  covering  the 
bedded  potatoes  with  chicken  wire.  On  top  of  this  the 
seed  are  covered  with  a  layer  of  2  inches  of  clean 
sand.  Frequently  the  seed  are  covered  with  4  or  5 
inches  of  sand.  This,  however,  is  a  mistake,  because  the 
deeper  the  seed  are  covered,  the  longer  and  tenderer  will 
be  the  shanks  of  the  sprouts.  This  will  mean  tender 
plants  which  may  be  susceptible  to  disease.  For  treat- 
ment of  the  seed  against  disease  see  p.  24. 

Covering  the  Hot-bed 

Many  growers  often  follow  the  practice  of  spreading 
a  2-to-3-inch  layer  of  fine  horse  manure  over  the  bed. 
This  serves  as  a  cover  to  preserve  the  heat  or  to  retain 
the  moisture.  When  the  sprouts  begin  to  appear,  pa.  c 
of  the  manure  is  removed  to  prevent  the  plants  from  be- 


Propagation  21 

coming  too  spindling  and  tender.  Many  growers  prefer 
the  use  of  a  layer  of  6  to  8  inches  of  pine  needles  or 
straw  instead  of  manure,  while  others  cover  the  bed 
with  dead  sweet  potato  vines  raked  off  and  preserved 
from  the  previous  season.  From  a  disease  considera- 
tion neither  manure  nor  dried  sweet  potato  vines  should 
be  used  as  a  cover  for  the  hot-beds.  Both  of  these  may 
carry  or  harbor  the  germs  of  black  rot  or  any  other  of 
the  fungi  which  cause  disease  in  the  sweet  potato. 
Throughout  the  Gulf  Coast  and  South-Atlantic  States 
it  is  not  always  necessary  to  cover  the  beds  for  the  pur- 
pose of  preserving  the  heat  or  protecting  the  plants  from 
cold.  In  the  Northern  States  where  sweet  potatoes  are 
grown,  glazed  hot-bed  sashes  3  by  6  feet  in  size  are 
greatly  in  use.  In  Delaware,  in  the  eastern  shores  of 
Maryland  and  Virginia,  as  well  as  in  many  of  the 
Southern  States,  a  light  canvas,  or  heavy  muslin  cover 
is  all  that  is  used  to  protect  the  hot-beds.  When  sashes 
are  used  they  are  made  to  slope  to  the  south  or  east 
where  the  greatest  amount  of  light  can  be  admitted. 
When  a  muslin  or  canvas  cover  is  used  it  is  supported 
on  lath  or  wire  so  that  the  rain  water  will  run  off  readily. 
During  bright  days,  the  canvas  or  muslin  is  rolled  up  to 
admit  sunlight  and  air.  Before  the  sprouts  are  "drawn," 
they  should  be  hardened.  This  is  done  by  gradually  re- 
moving all  glazed  or  canvas  covers.  The  sash  or  other 
covers  should  be  put  away  in  a  safe  and  dry  place,  so  as  to 
preserve  them  for  several  years'  use. 

Watering  the  Hot-bed 

Soon  after  the  sweet  potatoes  are  bedded  and  covered 
with  the  necessary  sand  the  bed  should  receive  a  thor- 
ough watering.    Later  waterings  are  determined  by  the 


22  The  Sweet  Potato 

dryness  of  the  soil.  The  quantity  of  water  required 
will  depend  upon  the  method  of  heating  used.  Manure- 
heated  beds  will  require  less  water  than  steam-or  flue- 
heated  beds.  The  beds  should  never  be  permitted  to  re- 
main soaked  for  long  periods,  as  this  will  weaken  the 
plants  and  encourage  disease,  nor  should  they  be  per- 
mitted to  remain  dry  too  long. 

It  is,  of  course,  more  convenient  to  have  water  under 
pressure.  Most  plant  growers  make  the  hot-beds  within 
the  city  or  town  limits  on  account  of  water  facilities. 
Where  potatoes  are  grown  on  a  large  scale,  a  well  is 
often  dug  and  the  water  pumped  into  an  elevated  tank 
or  a  series  of  barrels  (Fig,  3,  a),  which  are  connected 
by  watering  hose.  The  water  should  never  be  applied 
under  heavy  stream  pressure,  as  this  may  destroy  the 
beds  by  washing  out  the  roots  and  plants.  During  cool 
weather  the  beds  should  be  watered  during  the  warmest 
time  of  the  day.  In  warm  weather,  watering  in  the 
morning  is  more  desirable.  Wherever  possible,  it  is 
best  to  avoid  watering  the  beds  with  very  cold  water, 
as  the  chill  may  injure  the  sprouts. 

Other  Care  of  the  Hot-bed 

Growers  frequently  go  to  all  the  trouble  of  carefully 
selecting  and  of  treating  the  seed  for  disease,  but  violate 
all  rules  of  hygiene.  Diseased  sweet  potatoes  are 
thrown  about  indiscriminately,  and  the  rotted  material 
is  gradually  crushed  up  and  carried  about  by  the  wind, 
finally  finding  its  way  back  to  the  hot-bed.  Such  care- 
lessness should  never  be  permitted.  The  seed  should 
preferably  be  selected  for  freedom  of  disease  before 
they  leave  the  storage  house.  It  is  not  a  wise  policy  to 
take  the  seed  out  of  storage,  and  do  the  reselecting  near 


aju*:^.....^;* 


Fig.  3.    Pulling  Sprouts. 
a.  vShowinp;   water  system   arrariKcd    for  watering  sweet   potato  hotbeds. 
b.  Ideal  way  of  pulling  sweet  potat(i  sprouts. 


Propagation  23 

the  hot-beds.  With  this  method  diseased  material  is 
scattered  broadcast,  and  the  purpose  of  the  seed  treat- 
ment is  practically  defeated  by  infecting  the  soil  in  the 
hot-bed  from  left-over  and  discarded  roots.  All  dis- 
eased material  should  be  destroyed  by  fire,  buried  very 
deep,  or  cooked  and  fed  to  hogs  or  chickens.  When  the 
seed  is  brought  to  the  hot-bed  for  planting  it  should  be 
free  from  disease.  The  beds  should  not  be  allowed  to 
become  chilled ;  nor  should  they  be  overheated,  or  lack 
the  necessary  ventilation. 

Hot-bed  Troubles 

The  sweet  potato  root  is  a  very  common  carrier  of 
diseases.  Chief  of  these  troubles  which  may  be  men- 
tioned are  black  rot  (see  p.  141),  scurf  or  soil  stain 
(see  p.  150),  vine  wilt  or  stem  rot  (see  p.  154),  and 
foot  rot  (see  p.  139). 

Not  only  should  the  seed  be  selected  for  freedom 
from  disease  in  the  field,  but  this  should  be  done  again 
at  the  end  of  the  storage  season  and  before  planting. 
This  cannot  be  carried  out  without  a  knowledge  of  the 
diseases  which  affect  this  crop.  It  is  a  thousand  times 
easier  to  destroy  seed  which  carry  diseases  than  to  at- 
tempt later  to  control  these  diseases  when  they  have 
become  thoroughly  established  in  the  field.  Here  the 
old  dictum  "one  ounce  of  prevention  is  worth  two  of 
cure"  holds  true. 

It  is  to  the  interest  of  the  sweet  potato  grower  to 
plant  healthy  seed.  It  is  also  furthering  his  interest  and 
that  of  his  community  if  he  sees  that  no  diseased  seed 
is  brought  in  or  shipped  out  elsewhere.  Pure  seed  laws 
in  many  states  are  sadly  needed.  Unfortunately,  how- 
ever, for  the  grower,  the  unscrupulous  politician  is  fight- 


24  The  Sweet  Potato 

ing  them  with  all  his  might.    How  some  men  can  block 
such  needed  legislation  is  beyond  comprehension. 


Seed  Treatment  for  Disease 

It  should  be  stated  at  the  outset  that  if  seed  is  diseased 
there  is  no  cure  for  it.  The  sure  remedy  for  this  is  to 
destroy  by  fire,  or  to  boil  and  feed  to  stock.  The  seed 
treatment  here  recommended  is  only  a  form  of  insur- 
ance to  protect  the  healthy  roots  from  infection.  Black 
rot  may  always  be  detected,  because  this  disease  works 
on  the  surface  of  the  sweet  potato.  Roots  showing  this 
infection  should  not  be  used  for  bedding.  With  the 
stem  rot  or  wilt,  the  disease  can  not  always  be  detected 
by  a  surface  examination.  Seed  suspected  of  carrying 
this  disease  may  be  easily  tested  as  follows:  With  a 
sharp  knif^,  clip  the  stem  end  of  the  root.  A  white 
interior  surface  will  indicate  a  healthy  potato.  How- 
ever, if  the  interior  fibro-vascular  bundles  are  brown,  it 
is  a  sure  indication  that  the  seed  carries  disease,  and 
hence  should  be  discarded. 

Before  bedding,  and  after  the  seed  have  all  been 
selected  for  freedom  from  disease,  they  should  be 
soaked  for  ten  minutes  in  a  solution  of  one  ounce  of  cor- 
rosive sublimate  dissolved  in  eight  gallons  of  water. 
The  purpose  of  this  treatment  is  to  kill  all  the  germs  of 
disease  which  may  adhere  to  the  outside  coat  of  the 
sweet  potato. 

Corrosive  sublimate,  also  known  as  bichloride  of  mer- 
cury, will  corrode  metal  ware;  hence  it  should  only  be 
dissolved  in  wooden  vessels,  such  as  tubs,  tanks,  or  bar- 
rels (Figs.  4,  d  and  4,  e).  On  a  large  scale  enough  of  the 
solution  is  prepared  for  the  treatment  of  50  bushels  at 
one  time.     The  sweet  potatoes  are  placed  In  a  slatted 


Fig.  4.     Dipping  Sweet  Potato  Seed. 

a.  Diseased  swcel  potatoes  sjjrcatl  out  in  the  field  as  a  fertiliz.cr  (bad 
practiee).  b.  Pipe  ventilator  for  introducing  air  into  a  sweet  pf)tato  storage 
heating  system  placed  in  the  cellar.  The  pipe  is  uncovered  to  show  its 
outside  opening,  r.  Slatted  box  often  placed  in  the  renter  of  the  bin  for 
ventilation  purposes,  d.  Dipping  sweet  potatoes  in  woodin  d+ppin*,'  vats. 
e.   Dipping  sweet  potatoes  in  half  barrels. 


Propagation  25 

container  or  burlap  sack,  and  plunged  in  the  bichloride 
solution,  and  the  whole  is  submerged  for  ten  minutes. 
There  will  be  no  appreciable  harm,  if  the  potatoes  are 
left  a  few  minutes  longer  in  the  solution.  Where 
"safety  first"  is  the  rule,  this  should  not  be  done.  The 
bichloride  dissolves  more  readily  in  lukewarm,  than  in 
cold  water.  According  to  Weimer  (109),  each  bushel 
of  sweet  potatoes  treated  in  mercuric  chlorid  solution 
prepared  at  the  rate  of  one  ounce  of  the  bichloride  in 
eight  gallons  of  water  reduces  its  strength  by  one  per 
cent.  This  decrease  in  strength  of  the  mercuric  chlorid 
solution  is  due  largely  to  the  potatoes  and  to  the  dirt 
which  absorb  the  solution  during  the  treatment.  To 
offset  this  loss,  from  three-fifths  to  one-half  ounce  of 
mercuric  chlorid  and  sufficient  water  should  be  added 
to  make  the  solution  up  to  its  original  volume  after 
treating  10  bushels.  This  will  maintain  the  solution 
near  enough  to  its  original  strength  for  the  treatment  of 
50  bushels  of  sweet  potatotes. 

After  the  seed  have  been  soaked  in  the  bichloride 
solution  for  ten  minutes,  they  are  taken  out  imme- 
diately, and  the  excess  liquid  is  allowed  to  drain  off. 
They  are  then  ready  to  be  planted  at  once  in  the  hot-bed. 
In  fact,  the  treatment  should  immediately  precede  the 
bedding.  The  treated  seed  should  never  be  washed  with 
water,  as  to  do  so  will  remove  the  disinfectant  and 
defeat  the  purpose  of  the  treatment. 

Bichloride  of  mercury  is  a  violent  poison  when  taken 
internally.  The  bottle  containing  this  chemical  should 
be  conspicuously  labeled  Poison.  Care  should  be  taken 
that  no  farm  animals  or  children  are  allowed  to  drink 
by  mistake  from  the  solution  in  which  the  seed  are  to  be 
treated. 

Some  growers  believe  that  if  corrosive  sublimate  is 


26  The  Sweet  Potato 

a  poison,  then  any  other  chemical  poison  can  readily 
take  its  place.  The  author  has  actually  met  with  several 
cases  where  Paris  Green  was  used  instead  of  corrosive 
sublimate.  The  corrosive  sublimate  here  recommended 
is  used  to  kill  fungus  spores  only.  Paris  Green,  how- 
ever, is  used  only  to  kill  insects;  it  is  not  a  fungicide. 

Diseases  Affecting  Sprouts  in  the  Hot-bed 

It  becomes  self-evident  that  if  the  seed  are  diseased 
at  bedding,  these  same  troubles  will  be  communicated 
to  the  sprouts  later.  Health  and  vigor  in  the  seed  bed 
are  indicated  by  sprouts  with  deep  green  foliage.  This 
condition  is  to  be  met  with  where  sand  is  used  and 
where  the  seed  were  carefully  selected  and  treated  for 
disease.  Disease  in  the  seed  bed  is  usually  indicated  by 
a  paleness  of  the  tip  leaves,  a  general  pale  color  of  the 
entire  sprout,  and  cessation  of  growth.  Usually  the 
presence  of  disease  is  manifested  in  spots.  On  a  closer 
examination  we  may  find  that  the  diseased  spot  is 
restricted  to  the  sprouts  of  a  single  mother  root.  When 
the  latter  is  pulled  out,  it  will  usually  be  discovered  that 
the  rootlets  of  the  sprouts  have  either  rotted  away  or 
have  blackened.  This  condition  may  be  due  to  black  rot, 
In  more  severe  cases,  the  shanks  and  sometimes  the 
stems  of  the  sprouts  will  be  affected.  In  this  case,  the 
sprouts  are  stunted,  rotted  at  the  base,  and  have  little 
or  no  root  system.  Pale  spots  in  the  hot-bed  indicate 
presence  of  disease.  This  paleness,  however,  should  not 
be  mistaken  for  a  whitening  of  the  plants  when  kept 
covered  too  long  under  the  canvas.  If  this  is  the  case, 
the  plants  soon  regain  the  normal  deep  green  when  ex- 
posed to  the  sunlight.  There  are  some  growers  who 
insist  that  dead  or  blackened  rootlets  of  the  sprouts  are 


Propagation  27 

no  signs  of  disease,  but  that  these  are  due  to  the  scorch- 
ing of  the  heat  from  flues.  While,  as  already  stated, 
flues  often  burn  sprouts  in  the  bed,  yet  the  burning 
effect  is  indicated  more  as  a  browning  and  wilting  of  the 
rootlets  than  as  blackening,  which  is  so  characteristic 
of  the  black  rot.  Moreover,  diseased  spots  are  not  con- 
fined to  flue-heated  hot-beds,  but  they  are  very  common 
in  beds  heated  by  manure  or  by  hot  water.  In  fact, 
diseased  spots  are  a  common  occurrence  in  every  bed 
where  no  attention  is  paid  to  the  selection  of  the  seed 
or  to  seed  treatment.  Perfectly  healthy  sprouts,  when 
pulled  out,  possess  an  abundance  of  white  long  roots. 
It  is  only  where  such  plants  are  used  that  a  clean  crop 
is  to  be  expected. 

As  soon  as  disease  is  detected  in  the  hot-bed,  an 
area  including  infected  roots,  sprouts,  and  soil  should 
be  removed  and  replaced  by  clean  sand.  The  water 
should  be  withheld  slightly,  the  temperature  lowered, 
and,  if  possible,  plenty  of  ventilation  given.  If  there 
are  too  many  diseased  spots  in  the  bed,  it  should  be 
abandoned  and  its  sprouts  not  used. 

Certified  Seed 

There  is  an  increasing  demand  for  seed  sweet  pota- 
toes which  are  free  from  disease.  The  progressive 
grower  is  fully  alive  to  the  danger  of  buying  his  seed 
indiscriminately  and  of  taking  chances  of  introducing 
dangerous  diseases  to  his  field.  The  sooner  we  come  to 
demand  certified  seed  for  sweet  potatoes  as  is  done  with 
the  white  potato,  the  more  rapid  will  be  the  increase  in 
acreage  and  in  profitable  production.  The  state  of 
Arkansas  is  now  leading  in  educating  its  growers  to  the 
necessity  of  certified  seed.     The  system  employed  is 


28  The  Sweet  Potato 

described  in  Circular  No.  9,  1920,  of  the  Arkansas  State 
Plant  Board,  which  is  here  reproduced  as  a  sample  of 
what  may  be  done  by  other  states. 


Inspection  Service  in  Arkansas 

Application  for  Inspection 

Rule  45.  Any  person  growing  Irish  or  sweet 
potatoes  for  seed  may  have  such  seed  inspected  by 
applying  to  the  Chief  Inspector  on  or  before  March 
I,  for  the  inspection  of  spring  grown  seed  Irish 
potatoes  and  on  or  before  July  15  for  the  inspection 
of  seed  sweet  potatoes  or  fall  grown  seed  Irish 
potatoes.  Such  application  for  inspection  shall  set 
forth  (a)  the  location  of  the  place  where  the  seed 
is  grown  with  reference  to  the  direction  and  dis- 
tance to  the  nearest  railroad  station,  (b)  the  num- 
ber of  acres  to  be  inspected,  (c)  the  varieties  of 
potatoes,  (d)  the  distance  between  the  blocks  of 
growing  seed  stock  and  (e)  such  other  information 
as  the  Chief  Inspector  may  need  in  estimating  the 
time  required  for  inspection. 

Fees  for  Inspection 

Rule  46.  For  the  inspection  of  seed  Irish  or 
sweet  potatoes  as  provided  in  Rule  45,  the  Chief 
Inspector  shall  charge  fees  as  follows: 

(a)  A  fee  of  $5.00  to  be  paid  at  the  time  that 
the  application  for  inspection  is  made. 

(b)  An  additional  fee  of  $1.25  per  acre,  for 
each  acre  which  it  is  desired  to  have  certified.  The 
latter  fee  to  be  paid  before  the  second  inspection 
is  made. 

(c)  An  additional  fee  of  $5.00  for  each  extra 
inspection  which  may  be  warranted  as  a  result 
of  the  findings  of  a  previous  inspection. 


Propagation  29 

Applicants  must  furnish  the  inspector  trans- 
portation from  and  to  the  railway  station  and 
facilities  for  reaching  his  fields  of  seed  stock. 

Applicants  may  withdraw  their  applications  for 
inspection  by  notifying  the  Chief  Inspector  within 
15  days  after  receiving  from  him  the  report  on  the 
first  inspection. 

Requirements  for  Certification 

Rule  47.  All  seed  Irish  or  sweet  potatoes  for 
which  certificate  of  inspection  is  desired  must  be 
inspected  at  least  twice,  (a)  when  the  seed  crop  is 
growing  and  (b)  at  digging  time,  or  if  the  Chief 
Inspector  shall  so  elect,  after  the  potatoes  have 
been  stored.  Applicants  must  have  their  seed  crop 
in  a  clean  state  of  cultivation  and  in  such  condition 
otherwise  that  all  plants  can  be  easily  seen  by  the 
inspector. 

(c)  Upon  proper  fulfillment  by  the  grower  of 
the  seed  potatoes  of  all  requirements,  prescriptions 
and  conditions  set  forth  in  the  notices  issued  said 
grower  by  the  Chief  Inspector,  he  shall  be  issued  a 
certificate  of  inspection  in  form  as  hereinafter  set 
forth  in  the  rules  of  the  Board. 

Certification  of  Slips 

Rule  48.  The  Chief  Inspector  may  issue  a  cer- 
tificate of  inspection  covering  sweet  potato  slips  to 
any  person  who  shall  grow  his  sweet  potato  slips 
from  seed  sweet  potatoes  for  which  a  certificate  of 
inspection  was  issued  under  the  provision  of  Rule 
46  when  such  seed  sweet  potatoes  were  bedded  in 
accordance  with  directions  furnished  by  the  Board. 
Applications  for  a  certificate  under  the  provisions 
of  this  rule  must  be  made  to  the  Chief  Inspector 
30  days  before  the  sweet  potatoes  are  to  be  bedded, 
and  must  be  accompanied  by  a  fee  of  $1.00.    The 


30  The  Sweet  Potato 

sweet  potato  slip  certificate  shall  be  in  form  as 
hereinafter  set  forth  in  the  rules  of  the  Board. 

Labelling  Requirements 

Rule  50,  Holders  of  certificates  of  inspection 
granted  under  the  provisions  of  Rules  47  and  48 
of  the  Board  must  attach  to  each  carload,  sack, 
hamper,  basket  or  package  of  sweet  or  Irish  pota- 
toes or  sweet  potato  slips  covered  by  their  certifi- 
cate, a  tag  bearing  a  copy  of  said  certificate  with 
the  fac  simile  signature  of  the  Chief  Inspector. 
Said  tags  to  be  purchased  at  cost  from  Chief  In- 
spector. 

Whenever  a  holder  of  a  certificate  of  inspection 
as  provided  in  Rules  46  and  47  shall  sell  or  ship 
seed  sweet  or  Irish  potatoes  or  sweet  potato  slips 
which  are  not  covered  by  a  certificate  issued  by  the 
Chief  Inspector  of  the  Arkansas  State  Plant  Board 
he  shall  attach  to  every  carload,  sack,  hamper,  bas- 
ket or  package  of  such  sweet  or  Irish  potatoes  or 
sweet  potato  slips  a  tag  bearing,  in  letters  not 
less  than  %  in.  high,  (24  point  type)  the  words 
"Not  Covered  by  a  Certificate  of  Inspection  from 
the  Arkansas  State  Plant  Board." 

"All  Sales  of  Seed  and  Slips  Must  Be  Registered 

Rule  54.  Every  holder  of  a  certificate  granted 
under  the  provisions  of  Rule  47  or  48  of  the  Board 
must  file  with  the  Chief  Inspector,  at  the  end  of 
each  week,  a  copy  of  each  sale  or  disposition  of 
seed  or  slips  made  by  him  during  that  week. 

Each  invoice  shall  be  made  out  on  a  separate 
slip  (form  to  be  provided  by  the  Chief  Inspector) 
and  shall  set  forth  the  following  information: 

(a)  Name  of  the  certificate  holder  disposing  of 
the  seed  or  slips. 


Propagation  31 

(b)  Date  of  disposition  or  shipment 

(c)  Person  to  whom  the  seed  or  slips  are  dis- 
posed of. 

(d)  Number  of  bushels,  or  slips,  of  each  variety 
disposed  of. 

'(e)  If  seed  is  disposed  of,  whether  it  is  certified 

or  uncertified, 
(f )  If  certified  seed  or  slips  are  disposed  of,  the 
number  of  certificate  tags  used  for  the  sale 
or  shipment  must  be  recorded. 

Holders  of  certificates  must  also  account  for 
every  certificate  tag  purchased  from  the  Chief  In- 
spector and  all  unused  or  defaced  tags  must  be 
returned  to  the  Chief  Inspector  at  the  expiration  of 
the  certificate  of  which  the  tags  bear  a  copy. 

Seed  Certification 

The  first  inspection  for  certified  seed  is  made 
when  the  crop  is  in  the  field.  The  inspector  goes 
down  every  other  row  or  every  fourth  row  (de- 
pending upon  the  size  of  the  plants  and  on  the 
experience  of  the  inspector)  and  sees  every  hill.  If 
a  single  sweet  potato  hill  is  found  to  be  infected 
with  stem  rot  (wilt)  the  field  is  disqualified  for 
certification.  In  the  case  of  Irish  potatoes  the  field 
is  disqualified  if  more  than  five  per  cent  of  the  hills 
are  found  to  be  infected  with  "curley  top" 
(mosaic).  All  hills  infected  with  curley  top  must 
be  dug  up.  Fields  of  Irish  potatoes  infected  with 
wilt  will  be  rejected  for  certification.  All  fields  of 
Irish  or  sweet  potatoes  which  pass  the  first  inspec- 
tion are  eligible  for  the  second  inspection. 

The  second  inspection  is  made  at  digging  time 
or  else  after  the  potatoes  are  stored.  In  the  case 
of  sweet  potatoes  the  second  inspection  must 
show  the  potatoes  to  be  free  of  black  rot.    The 


32  The  Sweet  Potato 

second  Irish  potato  inspection  is  for  scab,  Rhizoc- 
tonia,  or  other  diseases.  Should  these  diseases 
appear  in  quantity  warranting  it,  a  certificate  will 
be  refused. 

In  addition  to  the  diseases  mentioned,  the  pres- 
ence of  any  other  diseases  may  disquahfy  the 
potatoes  for  certification  if,  in  the  opinion  of  the 
Chief  Inspector,  they  are  serious  enough  to  war- 
rant it. 

After  a  grower's  potatoes  have  passed  two 
inspections  he  is  granted  a  certificate  on  the  filing 
of  an  affidavit  in  form  as  shown  on  page  6.  A 
letter  from  the  Chief  Inspector  accompanies  each 
affidavit  and  makes  such  reservations  or  restric- 
tions as  the  particular  case  may  demand. 

Potatoes  may  be  reinspected  at  any  time  the 
Chief  Inspector  may  deem  it  necessary  and  on  the 
findings  of  such  extra  inspections  certificates  may 
be  revoked  or  additional  restrictions  may  be  im- 
posed. 

Slip  Certification 

No  inspection  is  made  for  the  certification  of 
sweet  potato  slips.  The  slips,  however,  must  be 
grown  from  seed  certified  by  the  Arkansas  State 
Plant  Board  and  the  seed  must  be  treated  and 
bedded  in  accordance  with  directions  furnished  in 
Type  Circular  No.  12.  No  slip  certificate  is  fur- 
nished to  any  one  who  grows  any  but  certified  slips. 
In  other  words,  the  applicant  for  a  slip  certificate 
must  either  grow  all  certified  slips  or  none. 

After  the  grower  has  followed  out  the  require- 
ments for  bedding  his  seed,  he  must  sign  an  affi- 
davit as  shown  on  page  7.  When  the  grower 
purchases  his  certified  seed  he  must  have  the  per- 
son from  whom  he  purchases  it  file  an  affidavit 
(form  furnished  by  Chief  Inspector)  showing  that 


Propagation  33 

the  certified  seed  was  actually  sold  to  the  applicant 
for  the  slip  certificate. 

Registration  Requirements 

In  accordance  with  the  provisions  of  the  Board's 
Rule  54  every  sale  of  seed  or  slips  which  is  made  by 
a  certificate  holder  must  be  registered  with  the 
Board.  Special  slips  are  provided  for  the  purpose, 
and  these  must  be  turned  in  once  a  week.  The 
object  of  this  rule  is  to  protect  the  certificate 
holders  and  also  the  purchasers  of  certified  seed 
against  the  misuse  of  a  certificate. 

Labelling  Requirements 

'  Because  of  the  fact  that  many  fields  of  potatoes 
are  disqualified  for  certification,  some  growers 
have  both  certified  and  uncertified  seed  for  sale. 
For  this  reason  Rule  50  of  the  Board  requires 
holders  of  certificates  to  label  every  sale  or  ship- 
ment of  their  seed.  If  the  seed  is  certified  it  must 
bear  a  tag  showing  copy  of  the  certificate  of  inspec- 
tion. If  the  seed  is  not  certified  it  must  be  con- 
spicuously labelled  in  accordance  with  the  pro- 
visions of  Rule  50  showing  that  it  is  not  certified  by 
the  State  Plant  Board. 


CHAPTER  III 

DRAWING  SPROUTS 

Ordinarily  the  "drawing"  of  sprouts  is  done  by 
unskilled  labor  or  by  children.  It  is  essential  that  the 
potato  grower  should  instruct  his  help  how  to  recog- 
nize diseased  plants  in  order  that  such  material  may  be 
prevented  from  finding  its  way  to  the  field.  It  will 
even  pay  to  have  reliable  helpers  reselect  all  the  pulled 
sprouts  and  discard  those  that  show  the  least  sign  of 
disease.  This  must,  of  course,  be  done  in  the  shade  and 
not  in  the  hot  sunshine.  It  is  expected  that  when  the 
sprouts  are  ready  to  be  transplanted  in  the  field  they  will 
be  free  from  disease,  for  ordinarily,  any  one  feeding  the 
sprouts  to  a  transplanting  machine  will  have  no  time 
to  discriminate  between  healthy  and  diseased  plants. 
In  drawing  the  sprouts  one  should  avoid  trampling  on 
the  seed  bed  as  far  as  it  is  possible  to  do  so.  This  is 
particularly  important  when  the  grower  expects  to  make 
more  than  one  pulling  from  his  bed.  Walking  on  the 
hot-beds  results  in  injury  to  the  mother  roots,  which 
opens  the  way  to  disease,  particularly  soft  rot.  Tramp- 
ling the  beds  may  be  avoided  by  placing  a  plank  for  the 
worker  to  sit  on  (Fig.  3,  b)  The  plank  is  moved  for- 
ward with  the  advance  of  the  pullers.  It  is  always  best 
to  set  the  sprouts  in  the  field  soon  after  a  rain.  The 
plants  are,  therefore,  pulled  soon  after  the  rain  and 
placed  in  crates  or  baskets,  and  covered  with  straw  or 
some  burlap  to  prevent  wilting.  When  "drawing"  the 
34 


Drawing  Sprouts  35 

plants,  one  should  hold  the  mother  potato  down  with 
one  hand,  and  remove  the  sprouts  with  the  thumb  and 
finger  of  the  other  hand.  If  several  plants  cling  to- 
gether, they  should  be  separated,  as  this  should  not  be 
left  for  the  planter  in  the  field  to  do. 

It  is  a  good  practice  to  puddle  the  plant,  that  is, 
plunge  the  roots  in  mud,  which  should  be  made  up  of 
water,  clay,  and  cow  manure,  and  stirred  until  it  forms 
a  thin  slime.  If  the  puddled  plants  become  dry  they 
should  be  repuddled  before  planting. 

Number  of  Draws  per  Hot-bed.  The  number  of 
draws  to  be  made  from  a  single  bed  usually  depends  on 
the  grower.  Some  prefer  but  one  pulling,  while  others 
make  two,  and  still  others,  and  particularly  those  who 
sell  sprouts,  make  three  draws.  The  best  sprouts  are 
naturally  those  of  the  first  pulling.  The  reason  is 
obvious,  since  the  sprouts  of  the  first  pulling  feed  on  the 
mother  roots,  which,  under  the  average  conditions,  are 
as  yet  sound.  After  the  first  drawing,  the  mother  roots 
are  nearly  always  disturbed  and  injured,  so  that  many 
soft-rot.  The  result  is  that  the  weak  sprouts  which  have 
now  been  left  over  must  shift  for  themselves,  which 
means  weaker  plants.  The  third  pulling,  therefore,  is 
often  of  a  decidedly  inferior  grade.  Not  only  is  there 
a  noticeable  difference  of  vigor  in  the  beds,  from  the 
first  to  the  third  pulling,  but  there  is  also  a  difference  of 
vigor  in  stand  in  the  field  from  these  pullings,  and  fur- 
thermore there  is  a  difference  in  the  keeping  qualities 
of  the  respective  yields  in  storage.  It  is  very  probable 
that  most  of  the  rotted  material  dumped  out  of  storage 
houses  could  be  traced  back  to  weak  sprouts  from  the 
third  pulling. 


36  The  Sweet  Potato 


Buying  or  Selling  Sprouts 

It  is  safest,  from  a  disease  consideration,  to  produce 
one's  own  seed  sweet  potatoes  and  sprouts.  Next  to 
that  it  is  far  safer  to  buy  seed  and  sprout  them  at  home 
than  to  buy  sprouts.  It  is  much  easier  to  judge  the 
quaUty  of  the  seed  when  bought,  than  it  is  to  judge  the 
sprouts,  for  in  this  case  the  quality  of  the  seeds  which 
produced  these  sprouts  is  unknown.  If  we  are  com- 
pelled to  buy  sprouts,  it  is  safest  not  to  order  them  from 
long  distances,  but  rather  to  secure  them  from  our  near- 
est neighborhood.  No  matter  how  well  sprouts  are 
packed,  they  must  suffer  a  severe  shock  from  travelling 
two  or  three  days  in  the  mails  or  by  express.  In  pre- 
paring the  plants  for  shipment,  it  is  best  to  bring  all  the 
"drawn"  sprouts  to  a  shed  where  the  plants  may  be 
tied  with  soft  string  in  bunches  of  lOO  each.  The  tips 
of  the  sprouts  should  always  be  dry  when  packed,  as 
otherwise  they  will  rot  when  shipped.  Damp  moss  or 
paper  may  be  wrapped  around  the  roots  in  the  crate  or 
basket,  but  the  tops  should  be  dry  and  given  ventilation. 

Cutting  Back  Sprouts.  Where  the  mother  roots  are 
planted  and  covered  too  deeply  in  the  hot-bed,  the 
shanks  of  the  sprouts  will  invariably  be  too  long.  As 
already  pointed  out,  there  is  little  to  be  gained  by  plant- 
ing a  sprout  with  a  long  shank.  Such  plants  are  tender 
and  usually  take  black  rot  in  the  field  much  more  quickly 
than  a  stocky  sprout  with  a  short  shank.  Shanks  longer 
than  two  inches  may  be  safely  cut  back  at  the  root  end 
without  any  injury  to  the  sprout.  This  is  particularly 
helpful  where  the  hand  planter  is  used. 

Dipping  Sprouts.  Work  by  the  author  (103)  has 
shown  that  it  is  not  necessary  to  dip  the  sprouts  after 
being  pulled  from  the  seed  bed  and  before  planting  in  the 


Drawing  Sprouts  37 

field.  This  Is  especially  unnecessary  where  clean  sand  has 
been  used  in  the  hot-bed  and  where  the  seed  have  been 
carefully  selected  and  treated  for  disease.  Dipping 
sprouts  in  the  same  strength  of  corrosive  sublimate  as  is 
recommended  for  the  seed  is  unsafe,  as  serious  injury 
may  result.  On  the  other  hand,  if  the  sprouts  are  merely 
dipped  and  taken  out  of  the  solution,  no  particular  bene- 
fit is  to  be  expected  and  this  will  only  entail  unnecessary 
labor  and  expense. 

Transplanting 

Transplanting  in  the  field  is  done  as  soon  as  the  soil 
is  warmed  up  and  danger  from  frost  is  over.  In  Vir- 
ginia, setting  out  is  begun  early  in  May  and  continues 
up  to  the  middle  of  June.  Duggar  (15)  states  that  the 
safest  time  to  set  out  sweet  potato  sprouts  for  an  early 
crop  is  as  follows :  Near  Jacksonville,  Fla.,  March  20 
to  April  I ;  in  South  Carolina,  Georgia,  Alabama,  Mis- 
sissippi, and  Arkansas,  April  i  to  25.  In  New  Jersey 
and  Delaware,  the  latter  part  of  May  is  the  best  time 
for  the  main  crop,  while  in  the  Gulf  states,  May  and 
June  are  best.  Very  early  planting  is  desirable  for  early 
marketing  at  high  prices.  For  the  main  crop  which  is 
to  be  stored,  transplanting  should  be  done  when  cool 
weather  is  over,  and  the  soil  warm.  For  early  potatoes, 
there  should  be  a  period  of  60  to  75  days  between  trans- 
planting and  digging. 

No  set  rules  can  be  laid  down  for  the  best  date  of 
transplanting.  This  will  depend  on  the  variety  and  the 
locality.  Experiments  on  the  Pumpkin  Yam  by  Stuckey 
in  Georgia  (see  Table  4)  show  that  year  in  and  year 
out  there  is  no  one  best  date  for  transplanting.  How- 
ever, under  Georgia  conditions,  light  yields  are  to  be 


38 


The  Sweet  Potato 


expected  when  transplanting  is  made  after  July  ist. 
The  latter  part  of  May  seems  to  be  about  the  best  time 
for  the  Pumpkin  Yam  type. 


Table  4 

Efects  of  Date  of  Planting  on  Yield  of  Pumpkin  Yam  Sweet 
Potato 


Pounds 

Pounds 

Total 

Date  Planted 

Marketable 

Small 

Pounds 

Potatoes 

Potatoes 

Potatoes 

April     23,  1910 

141 

71 

212 

April     30,  1910 

160 

67 

227 

May      12,  1910 

250 

55 

305 

May      24,  1910 

182 

56 

238 

;  une        I,  1910 

259 

73 

332 

June      II,  1910 

412 

63 

475 

.  une      21,  1910 
July         I,  1910 

275 

43 

328 

314 

54 

368 

July       15,  1910 

44 

H 

58 

July      30,  1910 

0 

4 

4 

May        6,  191 1 

410 

238 

648 

May      16,  191 1 

506 

271 

777 

May      26,  191 1 

241 

136 

377 

June        5,  1911 
June      15,  191 1 

258 

148 

406 

203 

95 

299 

June      25,  191 1 

185 

97 

282 

July        5,  191 1 

109 

88 

197 

July       15,  191 1 

146 

85 

231 

July       25,  19 II 

23 

12 

35 

May      20,  1913 

346 

88 

434 

May      30,  1913 

272 

86 

358 

June        6,  1913 

212 

70 

282 

June      19,  1913 

244 

62 

306 

June      28,  1913 

0 

178 

178 

July        7,  1913 

0 

106 

106 

July       17,  1913 

0 

34 

34 

.  uly      28,  1913 

0 

14 

14 

August    9,  19 13 

0 

0 

0 

Drawing  Sprouts  59 

Ridge  versus  Level  Culture.  Local  conditions  usually 
determine  whether  to  plant  on  low  or  high  ridges  or  on 
level  surface.  In  some  of  the  Southern  States,  where 
the  rainfall  is  uncertain,  ridge  culture  is  not  practiced. 
The  soil  moisture  is  rapidly  lost  from  high  ridges,  and 
this  is  not  the  case  with  low  ridges,  or  flat  surfaces. 
Ridge  culture  is  desirable  in  localities  with  high  rainfall, 
as  it  affords  good  drainage.  For  early  maturity,  ridge 
culture  is  the  general  practice,  for  the  reason  that  the 
soil  becomes  warm  sooner  than  it  otherwise  would. 

When  level  culture  is  practiced  the  rows  are  marked 
off  both  ways  with  a  cleated  roller  or  with  a  drag 
marker  run  by  hand;  or  by  one  horse.  The  plants  are 
set  out  at  the  intersections  of  the  marks,  that  is,  in  a 
28-inch  check,  to  allow  for  cultivation  in  two  directions. 
Where  ridge  culture  is  practiced,  the  ridges  are  made 
with  a  turn  plow.  In  rich  land  the  ridges  are  made  28 
to  30  inches  apart,  and  the  plants  set  14  to  18  Inches 
apart  in  the  row.  On  the  poorer  sandy  soils,  the  ridges 
are  2)^  to  48  inches  apart  and  the  plants  set  14  to  24 
inches  apart  in  the  row.  The  number  of  plants  per  acre 
should  be  determined  by  the  kind  of  soil  and  the  ferti- 
lizer used.  Varieties  with  heavy  vine  growth  will  nat- 
urally require  more  room  than  those  with  small  vine 
growth. 

The  method  of  setting  out  the  plants  will  depend  upon 
local  conditions.  The  essential  thing  is  to  set  out  a 
healthy,  well-hardened  sprout,  and  to  place  its  roots  in 
contact  with  moist  soil.  Much  water  Is  not  necessary 
at  the  time  of  transplanting.  About  half  a  pint  per  plant 
is  considered  sufficient.  However,  imder  climatic  con- 
ditions similar  to  those  of  New  Mexico,  irrigation  is 
recommended  as  soon  as  the  plants  are  set  out.  Ordi- 
narily when  the  hand  planter  (Fig.  2,  b)  or  the  trans- 


40  The  Sweet  Potato 

planting  machine  (Fig.  2,  a)  is  used,  the  amount  of 
water  is  automatically  regulated.  The  best  practices  in 
the  setting  out  of  sprouts,  regardless  of  the  method 
used,  are  given  by  Mooring  (70)  as  these:  The  roots 
are  placed  in  moist,  pulverized  soil;  the  openings  are 
made  large  enough,  so  that  the  roots  may  be  spread  out ; 
the  soil  is  pressed  firmly  about  the  roots.  Where  the 
roots  are  puddled,  the  mud  is  not  permitted  to  dry  on 
the  roots  before  they  are  planted. 

Tools  for  Transplanting.  On  a  small  scale,  where 
only  a  few  hundred  plants  are  set  out,  planting  by  hand 
will  answer  the  purpose.  Here  a  dibble  or  a  trowel 
could  be  used  to  advantage.  On  a  larger  scale,  however, 
setting  by  hand  is  very  tiresome,  and  hard  on  the  back. 
In  this  case  a  pair  of  wooden  tongs  may  be  used.  With 
this  instrument  the  plant  is  caught  by  the  root  and  thrust 
into  the  soil,  the  sprouts  being  carried  by  the  operator  in 
a  small  basket  strapped  to  the  waist.  The  tongs  possess 
a  spring  capable  of  throwing  the  jaws  apart,  and  are 
thus  held  in  one  hand  while  the  plants  are  inserted  with 
the  other.  Frequently,  in  connection  with  the  tongs,  an 
implement  known  as  a  shovel  is  also  used.  This  con- 
sists of  a  lath  sharpened  to  a  flat  point  and  is  used  to 
open  a  hole  in  the  soil  for  the  plant  to  be  set  in.  With 
this  implement,  the  plants  are  dropped  as  for  hand 
planting.  The  operator  who  does  the  planting  carries 
the  tongs  in  the  left  hand  and  the  shovel  in  the  right.  A 
hole  is  made  with  the  shovel  at  the  point  where  the 
sprout  is  to  be  set.  The  plant  is  then  picked  up  with  the 
tongs  and  inserted  in  the  hole,  and  the  earth  firmly 
pressed  around  with  the  foot  or  by  a  second  thrust  of 
the  shovel.  An  experienced  man  is  capable  of  setting 
out  ten  to  twelve  thousand  plants  in  a  day  with  these 
implements. 


Drawing  Sprouts  41 


Machinery 

Where  large  acreages  are  devoted  to  sweet  potatoes 
the  grower  relies  mostly  on  transplanting  machines 
(Fig.  2,  a).  The  main  features  of  these  consist  in  a 
device  to  open  a  small  furrow,  a  tank  to  supply  the 
water,  and  disks  and  blades  for  closing  the  soil  about 
the  plant.  To  operate  the  machine,  it  is  necessary  to 
have  a  steady  team,  and  two  well-trained  hands  who  can 
drop  the  plants  as  indicated  by  the  spacer  on  the  ma- 
chine. With  this  device,  the  plants  can  be  set  out  at  any 
season,  since  water  is  furnished  by  the  machine.  Under 
favorable  conditions  one  machine  will  set  out  3  to  4 
acres  per  day.  Most  transplanting  machines  are  de- 
signed either  for  ridge  or  level  culture. 

Replacing  Dead  Hills.  It  is  not  uncommon  to  find 
many  dead  hills  soon  after  transplanting  in  the  field. 
Before  replacing  missing  plants  one  should  determine  the 
cause  of  their  dying.  Cut  worms  often  do  considerable 
damage,  but  these  should  not  be  tolerated,  as  they  may 
be  controlled  with  poisoned  bait.  Hills  killed  by  cut 
worms  or  by  frost  may  be  replaced.  However,  if  it  is 
found  that  the  plants  died  from  black  rot  or  "stem  rot" 
no  attempt  should  be  made  at  replacing.  (For  symp- 
toms of  these  two  diseases  see  pp.  141  and  154). 
Healthy  sprouts,  when  set  out  in  diseased  hills,  will 
readily  contract  these  diseases  themselves.  Sprouts  will 
usually  die  soon  after  transplanting,  if  the  soil  is  in- 
fected or  the  plants  were  diseased  to  begin  with.  Both 
of  these  conditions  should  be  avoided. 


42  The  Sweet  Potato 

Soil  Requirements 

The  best  sweet  potato  soil  is  a  sandy  loam  with  a 
clay  subsoil.  Under  these  conditions,  harvesting  is 
easy,  and  the  quality  and  appearance  of  the  potatoes  are 
very  desirable. 

In  heavy  soils  the  roots  are  rough  and  have  a  tend- 
ency to  crack  during  active  growth  in  wet  seasons. 
Stiff  clay  soils  tend  also  to  produce  heavy  vine  growth, 
and  long  irregular  roots,  which  are  inclined  to  be 
watery;  hence  difficult  to  cure  and  keep.  Dark  muck 
soils  may  be  adapted  for  sweet  potatoes,  provided  they 
are  well  drained  and  thoroughly  worked.  Sweet  pota- 
toes often  thrive  well  in  clean  sand,  where  commercial 
fertilizer  has  been  added.  Fair  yields  may  be  expected 
on  worn-out  cotton  and  tobacco  lands  in  the  South,  pro- 
vided a  good  system  of  rotation  is  adopted,  and  a 
leguminous  crop  turned  under  to  add  humus  to  the  soil. 
Sweet  potatoes  are  well  adapted  to  newly  cleared  timber 
land,  such  as  cut-over  pine  land  in  the  South.  However, 
in  this  case,  it  is  far  more  advisable  to  grow  a  corn  crop 
the  first  year  and  then  follow  it  with  sweet  potatoes.  In 
newly  cleared  land  the  roots  of  trees  and  stumps  will 
greatly  interfere  with  thorough  cultivation  of  the  sweet 
potato. 

When  sweet  potato  land  is  chosen,  its  drainage  should 
not  be  overlooked,  as  this  is  very  essential  for  the  best 
results.  The  surface  soil  should  be  six  to  eight  inches 
deep,  and  underlaid  with  a  porous  clay  subsoil  capable 
of  carrying  off  the  surplus  water,  and  yet  of  preventing 
the  leaching  out  of  the  fertilizers  which  are  applied 
every  year.  Deep  surface  soil  with  a  sandy  or  very 
porous  subsoil  should  be  avoided  for  sweet  potatoes. 
Such  a  land  will  produce  long  stringy  potatoes,  which 


Drawing  Sprouts  43 

are  unfit  for  the  market.  On  the  other  hand,  there  is 
no  objection  to  a  shallow  surface  soil,  as  it  may  be 
deepened  every  year  by  cultivation. 

Together  with  soil  considerations,  we  must  remem- 
ber that  the  sweet  potato  is  very  sensitive  to  frost.  It 
should,  therefore,  be  planted  on  the  more  elevated  sec- 
tions of  the  farm.  This  will  secure  the  longest  growing 
season,  make  possible  early  planting,  and  insure  a  longer 
fall  season  for  the  final  maturity  of  the  crop. 


Preparation  of  the  Soil 

In  the  rich,  sandy  loams,  it  is  not  uncommon  for  most 
of  the  potatoes  to  grow  to  the  jumbo  size.  These  are, 
of  course,  disliked  by  the  market,  and  the  grower  is 
always  confronted  with  the  difficulty  of  disposing  of 
his  crop.  Rich,  sandy  lands,  which  produce  large  pota- 
toes, should  be  plowed  shallow,  not  over  three  to  four 
inches  deep.  Stiffer,  less  porous  soils  should  be  plowed 
deeper  with  a  two-horse  turning  plow  to  "break  it 
broad-cast"  so  as  to  prevent  the  formation  of  small 
potatoes,  altogether.  This  is  usually  done  in  the  spring, 
and  is  followed  by  a  cross  discing;  that  is,  the  land  is 
disced  both  ways,  if  it  is  level.  On  terraces,  this  cannot 
be  done.  In  light  soils,  one  discing  should  be  sufficient. 
The  disc  harrow  is  then  followed  up  with  a  spring  tooth, 
acme,  or  spike  tooth  harrow.  This,  however,  is  done 
only  where  the  plants  are  set  out  in  flat  rows. 

Rotation 

From  the  standpoint  of  disease  control,  increased  pro- 
duction, and  soil  improvement,  the  best  results  are  ob- 
tained with  sweet  potatoes  where  a  careful  system  of 


44  The  Sweet  Potato 

rotation  is  adapted.  Careful  seed  selection  and  a  rota- 
tion where  sweet  potatoes  will  grow  on  the  land  every 
third  or  fourth  year,  will  tend  to  eliminate  dangerous 
diseases.  By  this  method  black  rot,  foot  rot,  stem  rot 
or  wilt,  and  pox,  will  be  prevented  from  becoming  per- 
manently established  in  the  land.  No  rotation  is  com- 
plete if  it  excludes  a  leguminous  or  other  green  cover 
crop  to  be  worked  in.  Cowpeas,  soy  beans,  velvet  beans, 
or  crimson  clover,  as  they  are  variously  adopted,  will 
make  good  cover  crops.  In  Virginia,  Maryland,  Dela- 
ware and  New  Jersey,  when  the  potatoes  are  dug  for 
early  market,  crimson  clover  may  be  sown  as  a  cover 
crop  after  the  sweet  potatoes.  This  is  possible  only  if 
the  potatoes  are  off  by  September  ist  to  the  15th  in 
New  Jersey,  Delaware,  and  Maryland ;  and  by  Septem- 
ber 30th  in  southern  Virginia.  If  the  potatoes  are  dug 
too  late  for  planting  crimson  clover,  a  cover  crop  of 
rye,  oats,  or  vetch  will  offer  an  acceptable  substitute. 

Although  no  fast  rule  can  be  laid  down,  the  rotation 
advised  by  Miller  (69)  is  here  recommended  and  is  as 
follows : 


FOR   THE    COTTON    BELT    WHERE    SWEET    POTATOES   ARE 
GROWN  AS  A  FARM  CROP 

A.  First  year. 

a.  Cotton,  followed  by  rye  for  winter  pasture  or 
as  a  crop  to  turn  under ;  or 

b.  Corn,  with  cowpeas  or  velvet  beans  planted  as  a 
soil  improving  crop. 

Second  year.     Sweet  potatoes,  followed  by  winter 

cover  crop  of  rye,  or  oats  and  vetch. 

Third  year.    Oats,  followed  by  peanuts  or  cowpeas. 

B.  First  year. 


Drawing  Sprouts  45 

Sweet  potatoes,  followed  by  a  winter  crop  of  rye, 
or  oats  and  vetch. 

Second  year.     Cotton,  with  rye  sown  between  the 
rows  for  winter  pasture  or  to  turn  under. 
Third  year.     Corn,  with  cowpeas  or  velvet  beans 
planted  as  a  soil  improving  crop. 


FOUR-YEAR  ROTATION  FOR  THE  SOUTHERN  SWEET 
POTATO  SECTION 

First  year.     Sweet  potatoes. 

Second  year.  Winter  oats,  followed  by  peanuts 
or  cowpeas. 

Third  year.    Cotton. 

Fourth  year.  Corn,  with  cowpeas  or  velvet  beans 
between  the  rows. 


THREE-YEAR    ROTATION    FOR    THE    EASTERN    SHORE    OF 
VIRGINIA  AND  MARYLAND 

First  year.  Sweet  potatoes,  followed  by  crimson 
clover  or  rye  as  a  winter  crop. 

Second  year.  Early  Irish  potatoes.  On  many 
farms  corn  is  planted  between  the  rows  of  potatoes  at 
last  cultivation;  on  other  farms  the  potatoes  are  fol- 
lowed by  fall  vegetables. 

Third  year.  Winter  oats,  followed  by  cowpeas  for 
hay. 

Chemical  Fertilizers 

Sweet  potatoes,  as  every  other  crop,  do  remove  cer- 
tain fertilizing  elements  from  the  soil.  This  is  shown 
in  Table  5  by  Keitt  (58). 


46 


The  Sweet  Potato 


Table  5 
Fertilizing  Elements  Removed  by  a  Crop  of  Sweet  Potatoes 


Variety 

Bushels 
Acre 

Total 
Per  Cent 

Acid 
Phosphate 

Per 

Cent 

Nitro- 
gen 

Equiv- 
alent to 
Ammo- 
nia 

Per 

Cent 

Potash 

Value 
Removed 

Acre 

Nancy  Hall 

270.0 
281.0 
416.0 
141. 0 
191. 0 
450.0 
158.0 
281.0 
214.0 
180.0 

270.0 
174.0 
141. 0 
326.0 

0.0573 
0.0768 
0.0775 
0.0798 
0.0773 

0.0869 

0.0435 
0.0519 
0.0525 

0.0840 
0 . 062 1 
0.0893 
0.1069 

0.280 
0.243 
0.243 
0.236 
0.214 
0.271 
0.266 
0.245 
0.213 
0.292 

0.348 
0.184 
0.231 
0.283 

0.332 
0.295 
0.295 
0.287 
0.260 
0.329 
0.323 
0.298 
0.259 
0.355 

0.423 
0.229 
0.281 
0.344 

0.445 
0.479 
0.492 
0.434 
0.388 

0.534 
0.519 
0.343 
0.390 
0.506 

0.684 
0.336 
0.392 
0.382 

$11.75 
11.83 
16.72 

20.69 
7.26 

10.55 
7.62 

8.54 

16.04 

5-51 

5.45 

14.82 

Polo 

Southern  Queen 

White  Spanish 

General  Grant 

Arkansas  Beauty 

Tennessee  Notchleaf . 
Yellow  Nancemond. . 

Purple  Yam 

Pumpkin  Early  Yel- 

Shanghor  Yam 

Vineland  Bunch  Yam 
Fulleton  Yellow  Yam. 

Average 250  bu. 

$10.73 

Cost  of  fertilizer  removed  per  bushel $  o .  043 


The  judicious  use  of  commercial  fertilizer  will  insure 
increased  yields.  No  fast  or  hard  rule,  however,  can 
be  laid  down  as  to  kind  and  quantity.  These  two  things 
will  largely  depend  on  the  soil  requirements  and  on 
climatic  conditions.  In  the  Northern  States  where 
sweet  potatoes  are  grown,  the  crop  must  mature  in  the 
shortest  possible  time.  Here  then,  heavy  application  of 
a  high-grade  commercial  fertilizer  is  practical.  A'  fer- 
tilizer analyzing  2  to  4   per   cent  available   nitrogen, 


Drawing  Sprouts  47 

8  per  cent  phosphoric  acid,  and  If  possible,  8  to  10  per 
cent  potash  should  give  good  results,  for  this  Is  really 
a  rich  mixture.  However,  with  the  present  scarcity  of 
potash,  it  is  omitted  altogether  or  used  In  amounts  of 
I  or  2  per  cent.  The  quantity  of  fertilizer  to  apply 
should  depend  upon  the  fertility  of  the  soil  and  the  sys- 
tem of  crop  rotation  used.  In  New  Jersey,  Maryland, 
Delaware,  or  Virginia,  It  Is  not  uncommon  for  growers 
to  apply  1000  to  1500  pounds  per  acre,  either  broadcast 
or  in  the  row. 

In  the  sandy  loams  of  the  South,  where  the  season  is 
long,  and  the  climate  well  adapted,  the  application  of 
high-grade  fertilizer  is  not  always  essential.  Fair  re- 
turns may  be  expected  from  the  use  of  a  fertilizer  which 
consists  of  one  part  of  cottonseed  meal  to  two  to  three 
parts  of  16  per  cent  acid  phosphate  drilled  In  the  rows 
at  the  rate  of  500  to  600  pounds  per  acre. 

To  prevent  Injury  from  burning,  the  fertilizer  should 
be  applied  a  week  to  ten  days  before  planting.  In  very 
poor  lands,  or  where  level  culture  is  practiced,  the  fer- 
tilizer should  be  applied  broadcast  and  at  a  high  rate. 
In  the  better  lands,  and  where  the  plants  are  set  in  beds 
on  ridges,  it  is  usually  applied  in  the  row  with  a  one- 
or  two-horse  fertilizer  sower. 

It  has  seemed  to  be  the  general  belief  of  both  growers 
and  horticulturists  that  potash  is  very  essential  In  the 
production  of  sweet  potatoes.  It  is  the  belief  of  the 
author  that  this  was  often  over-estimated  and  more 
potash  was  used  than  the  crop  could  utilize.  This  is 
substantiated  by  Duggar  and  Williamson  (16),  who 
found  that  phosphate  and  nitrogen  were  much  more 
important  than  potash,  as  is  shown  in  Table  6. 


48 


The  Sweet  Potato 


1 

w 

OlOO 

to       00       00 

%  i  i 

o      o 

S 

tg 

w 

"S  O^Tt       0>      (O        O            00        «             o                   o> 

o> 

ll|i 

TfTj-      00       lO       00           <£>      <o            t                «o 
to  •*      o      «o       «           »7      °           ®              «>. 
lo  M      00       «       o            r<i      t^           r-               o» 

tDTfTl-t--t              -"l-t^              «                   00 

•§  to      00      t-     00           N      r-          o               r-. 

■§  CTicO        4      to       M            ro      00             ro                 r^ 
awt^OOtOOO             oof              M                   U3 

llj^l 

"Stooto       m      MM       ro      t-          o      cr>     <o 

aovocooo       in      Wirt      lo      t          n      ^      o 
CqtfONM      ■*      Ttfo      t      >o          lo      ■*     to 

M 

till 

flip 

|>0«     .  M       to        00     .         N         f.               O           .         ^ 

i*l 

■oiotJ^r-.      o      ttwi      moo           t^to       «t 

3i 

ilii 

|iiP 

il|*^ 

•gWrOf*        T)-       tOtO        >0        t»              t~        0>       <0 

•^HOCTiio      \n     oo'to'     to      fo          ro     oo'      d 
2  tf  w  fooo      N      awt      N      t         t-     00      »o 
Shmmh       m       mh       «       «            «       w       « 

11 

ill 
Hi 

'I 

1il 

111 

'1 

i 

1 

li 
11 

2^ 

1- 
I 

o 

1 

1 

OS 

1 
■3 
B 
$ 

Amount 
Fertil- 
izer 
per 
Acre 

III  liiii  iiiiiiii  III 

i« 

M   etc 

tl 

to    to 

00 

O) 

o 

S 

p 

1 

Drawing  Sprouts 


49 


From  Table  7  it  is  seen  that  nitrogen  and  phosphoric 
acid  brought  about  equal  average  increases. 


Table  7 

Increase  in  Bushels  oj  Sweet  Potatoes  per  Acre  Due  to  an 

Application  of  400  Pounds  of  Cottonseed  Meal,  or  480 

Pounds  Acid  Phosphate,  or  400  Pounds  Kainit 


1912 


1913 


1914 


Average 
increase 
3  Years 


Increase  of  sweet  potatoes  per  acre 
when  cottonseed  meal  was  added 

To  imfertilized  plot 

To  acid  phosphate  plot 

To  kainit  plot 

To  acid  phosphate  and  kainit  plot, . 
Average  increase  with  cottonseed 
meal 


of  sweet  potatoes  per  acre 
when  acid  phosphate  was  added: 

To  unfertilized  plot 

To  cottonseed  meal  plot 

To  kainit  plot 

To  cottonseed  meal  and  kainit  plot. . 
Average  increase  with  acid  phos- 
phate   


of  sweet  potatoes  per  acre 
when  kainit  was  added: 

To  unfertilized  plot 

To  cottonseed  meal  plot 

To  acid  phosphate  plot 

To  cottonseed  meal  and  acid  phos- 
phate plot 

Average  increase  with  kainit . . . 


1.7 
6.5 
4.6 
9.0 

5-5 


70.9 
75-7 
20.2 
24.6 

47.8 


41-7 
44.6 
-  9.0 

•  6.5 
17.7 


Ii8. 

46. 
-II, 

50. 


50.9 


77-2 

5.0 

-131 

48.4 

29.4 


80.3 
-49.8 

-lO.O 

-  6.4 
3.5 


119. 4 
58.7 

-  30 
65.5 

60.2 


78.0 

173 

-  1.6 

66.9 

40.2 


84.8 
-37.6 

5-2 

12.0 

16. 1 


79-9 
37-2 
•  3-3 
41.5 

38.9 


75-4 

32.7 

1.8 

46.6 

39-1 


68.9 
-14.3 

-  4.6 

-  0.3 
12.4 


Kainit  at  the  rate  of  400  pounds  per  acre  had  little 
or  no  effect  in  increasing  the  yield  when  used  with  other 
fertilizers,  though  when  used  alone  it  increased  the  yield, 


50 


The  Sweet  Potato 


almost  as  much  as  cottonseed  meal  or  acid  phosphate. 
However,  before  these  figures  are  universally  adopted, 
more  experiments  are  necessary  in  all  the  sweet  potato 
states  of  both  North  and  South  to  determine  the  true 
value,  if  any,  of  potash  in  the  production  of  this  crop. 

While  fertilizers  exert  a  beneficial  effect  in  increasing 
production,  it  fluctuates  in  some  years  more  than  in 
others.  This  is  clearly  shown  from  the  work  of 
Stuckey  (93). 

The  area  devoted  to  this  experiment  which  was  con- 
ducted from  1908  to  191 3,  inclusive,  was  divided  into 
six  plats  of  one-thirtieth  of  an  acre  each.  The  variety 
used  was  the  Pumpkin  Yam.  The  fertilizer  treatments 
were  as  indicated  in  Table  8,  which  also  gives  the  rel- 
ative yields,  and  the  subsequent  effect  of  the  fertilizers 
on  the  amount  of  rots  in  storage. 

Table  8 

Yields  from  Fertilizer  Plots  of  Sweet  Potatoes  from  igo8  to 
1913 


Plot  No. 

Yields  per  Plot 

Bushels 
Acre 

Per  Cent 

and  Kind 

of 

Fertilizer 

Used 

Pounds 
Marketable 
Potatoes 

Pounds 

Small 

Potatoes 

Pounds 
Total 

Rot 
During 
Winter 

1908 


I 

267 

25 

292 

159-2 

16.0 

2 

336 

21 

357 

194- 7 

26.5 

3 

333 

25 

358 

195-2 

4-5 

4 

286 

28 

314 

171. 2 

II. 5 

5 

342 

28 

370 

201.8 

II. 0 

6 

332 

33 

365 

199-0 

6.0 

Drawing  Sprouts 


51 


Table  8 — Continued 


Plot  No. 

and  Kind 

of 

Fertilizer 
Used 


Yields  per  Plot 


Pounds 
Marketable 
Potatoes 


Pounds 

Small 

Potatoes 


Pounds 
Total 


Bushels 
per 
Acre 


Per  Cent 

Rot 
During 
Winter 


1909 


I 

211 

71 

282 

153.8 

8.5 

2 

233 

57 

290 

1581 

19.2 

3 

240 

75 

315 

171. 8 

II. I 

4 

145 

53 

198 

108.0 

5 

271 

75 

346 

188.7 

8.8 

6 

251 

68 

319 

1740 

8.5 

I9I0 


I 

205 

71 

276 

150.5 

17.6 

2 

235 

53 

288 

157.0 

14.4 

3 

253 

60 

313 

170.7 

12.4 

4 

^P 

67 

212 

115. 6 

9.4 

5 

281 

90 

371 

202.3 

15.3 

6 

250 

84 

334 

182. 1 

5.8 

1911 

I 

226 

lOI 

1    327 

178.3 

38.8 

2 

224 

55 

279 

152. 1 

29.0 

3 

220 

276 

150.5 

31-I 

4 

147 

84 

231 

126.0 

41.2 

5 

235 

105 

1    340 

185.4 

36.7 

6 

178 

73 

1    .5. 

136.9 

14. 1 

I9I2 


I 

248 

138 

386 

210.5 

16.0 

2 

212 

59 

271 

147.8 

7-7 

3 

202 

54 

256 

139.6 

9.0 

4 

171 

79 

250 

136.3 

13.9 

5 

195 

108 

303 

165.2 

10.9 

^ 

166 

68 

234 

127.6 

12.2 

52 


The  Sweet  Potato 

Table  8 — Continued 


* 
Plot  No. 

Yields  per  Plot 

Bushels 
Acre 

Per  Cent 

and  Kind 

Fertilizer 
Used 

Pounds 
Marketable 
Potatoes 

Pounds 
Small 
Potatoes 

Pounds 
Total 

Rot 
During 
Winter 

I9I3 


I 

322 

129 

451 

246.0 

15.8 

2 

359 

66 

425 

231.8 

32.5 

3 

270 

76 

346 

188.7 

32.5 

4 

187 

94 

281 

153-2 

19.1 

307 

122 

429 

234.0 

17.5 

^ 

307 

75 

382 

208.3 

38.3 

Fertilizer  per  Acre 

* 

1 24  tons  stable  manure 

2 2100  pounds  16  per  cent  phosphoric  acid 

3 900  pounds  sulphate  of  potash 

4 1500  pounds  nitrate  of  soda 

5 1800  pounds  complete  fertilizer 

6 check,  no  fertilizer 

It  is  seen  from  the  foregoing  table  that  with  the  ex- 
ception of  19 1 3,  there  was  a  gradual  decline  in  yields  in 
all  plats  from  1908  to  1912,  irrespective  of  fertilizers  ap- 
plied. In  1913  there  was  a  sudden  rise  in  yield.  This  may 
perhaps  be  due  to  climatic  variations  from  year  to  year. 
These  data  definitely  show  that  no  reliable  conclusions 
can  be  drawn  from  one  or  two  years'  trials  with  ferti- 
lizers. It  is  further  shown  in  Table  8  that  the  percent- 
age of  rot  from  the  different  plats  varied  from  year  to 
year  to  such  an  extent  that  It  could  not  be  said  with  cer- 
tainty that  the  keeping  qualities  of  sweet  potatoes  were 
in  any  way  influenced  by  the  kind  of  fertilizer  used. 

For  poor  soils,  Duggar  recommends  the  following 
formulas  of  fertilizers,  the  particular  choice  of  which 


Drawing  Sprouts 


S3 


will  depend  mainly  on  the  land  itself.    These  formulas 
are  shown  in  Table  9  and  are  self-explanatory : 

Table  9 

Fertilizer  Formulas  for  Sweet  Potatoes 


Kind  and  Amount  of  Fertilizer  per 
Acre 

Nitro- 
gen 

Avail- 
able 
Phos- 
phoric 
Acid 

Potash 

150  pounds  of  nitrate  of  soda 
350  poirnds  superphosphate 
150  pounds  muriate  of  potash 

I 

Pounds 
24 

Pounds 
41 

Pounds 
77 

280  pounds  dried  blood 

320  pounds  boneblack 

160  pounds  miiriate  of  potash 

II 

29 

53 

82 

100  pounds  nitrate  of  soda 

160  pounds  boneblack 
80  pounds  sulphate  of  potash 
ID  tons  barnyard  manure 

III 

114 

27 

"3 

360  pounds  cottonseed  meal 
320  pounds  superphosphate 
640  potmds  kainit 

IV 

26 

43 

94 

Stable  Manure 

To  thrive  well,  sweet  potatoes  require  plenty  of 
humus  in  the  soil.  This  is  often  supplied  by  the  appli- 
cation of  stable  manure  or  compost.  Fresh  manure 
should  never  be  applied  direct  during  the  preparation 
of  the  land  for  planting.  This  will  increase  the  expense 
of  weeding,  and  in  dry  seasons  the  plants  will  suffer 


54 


The  Sweet  Potato 


from  drought.  The  manure  should  be  applied  to  the 
previous  crop  as  is  practiced  in  New  Jersey,  where  it  is 
broadcasted  in  the  fall,  and  applied  at  the  rate  of  lo  to 
15  tons  per  acre.  Manure  should  not  be  used  on  lands 
affected  with  soil  stain  {Monilochaetes  infuscans),  or 
with  pox,  also  known  as  ground  rot  (Cystospora 
batata).  Numerous  growers  are  in  the  halDit  of  com- 
bining horse  manure  with  chemical  fertilizers.  Table 
10  by  Price  shows  that  the  net  gain  from  the  combina- 
tion of  small  quantities  of  the  manure  and  chemicals 
was  only  $5.36  per  acre.  Twenty  tons  of  manure  per 
acre  both  alone  and  in  combination  with  full  quantities 
of  chemical  fertilizer,  though  increasing  the  yield,  re- 
sulted in  a  considerable  loss.  However,  these  figures 
could  mean  but  little  because  the  experiment  was  run 
only  two  years,  and  perhaps  on  soils  not  responsive  to 
treatment. 

Table  10 

Value  of  Crop  from  Different  Fertilizers 


Cost 

of 

Fertilizer 

Net 

Value 

of  Crop 

per  Acre 

Net 

Gain  or 

Loss 

Average  Net 

Gain  or 

Loss  for 

Two  Years 

No  fertilizer.    ... 

.... 

$113-33 

Manure    and    chemicals, 
one-half 

$26.17 

$118.69 

$  5.36gain 

$20. 02  gain 

Manure    and    chemicals, 
whole 

$52.34 

$92.43 

$20 . 90  loss 

$  2. 44 loss 

$40.00 

$106.76 

$  6. 57 loss 

$  i.ooloss 

Drawing  Sprouts  55 


Green  Manure 

Where  manure  is  scarce,  the  soil  humus  may  be 
secured  through  the  use  of  green  cover  crops.  Legumes, 
such  as  crimson  clover,  cowpeas,  soy  beans,  vetch,  and 
velvet  beans,  will  make  ideal  green  manures  when 
worked  under.  In  the  northern  sweet  potato  states, 
crimson  clover  is  sown  between  corn  rows  at  the  last 
cultivation.  The  clover  usually  makes  a  good  growth 
early  in  the  spring  and  is  plowed  under  when  the  land 
is  prepared  for  sweet  potatoes.  In  those  parts  of  the 
Southern  States  where  crimson  clover  does  not  thrive, 
velvet  beans,  cowpeas,  or  rye  will  give  good  results. 


Lime  or  Hardwood  Ashes 

The  use  of  lime  on  sweet  potato  soil  is  largely  deter- 
mined by  the  grower's  own  inclinations.  On  poor  soils, 
or  where  green  manure  tends  to  sour  the  soil,  the  appli- 
cation of  lime  will  be  beneficial.  Lime  should  be  used 
indirectly,  and  preferably  in  a  three-year  rotation  at 
the  rate  of  one  to  two  thousand  pounds  of  burned  lime 
per  acre.  It  is  best  applied  after  plowing  under  a  green 
crop,  or  to  the  crop  preceding  sweet  potatoes.  Burned 
lime  should  at  first  be  air  slacked. 

Hardwood  ashes  are  scarce  and  difficult  to  secure. 
When  easily  available,  unleached  wood  ashes  applied 
broadcast  at  the  rate  of  1200  to  1500  pounds  per  acre 
may  take  the  place  of  lime.  In  no  case,  however,  should 
either  lime  or  wood  ashes  be  applied  to  soil  infected  with 
pox.  Where  this  is  done,  the  disease  greatly  increases 
and  the  yields  are  reduced. 


56 


The  Sweet  Potato 


Effect  of  Fertilizers  on  Vine  Growth 

It  is  generally  believed  that  the  use  of  certain  fer- 
tilizers will  produce  more  vine  growth  in  proportion  to 
the  yield  of  potatoes.    Table  ii  by  Stuckey  (93)  shows 


Table  ii 
Effect  oj  Fertilizer  on  Vine  Growth 


Plat 
No. 

Fertilizer  Used 

Pounds 
Green  Vines 

Pounds 
Potatoes 

1226 
422 
282 
716 
661 
226 

451 
425 
346 
381 
429 
382 

3 

4 
5 
6 

Sulphate  of  potash 

Nitrate  of  soda     

Complete  fertilizer               . . 

Check,  no  fertiUzer 

that  stable  manure  alone  gave  a  heavy  crop  of  vines  and 
a  heavy  crop  of  potatoes.  The  nitrate  of  soda  gave  a 
heavy  crop  of  vines  but  a  light  crop  of  potatoes. 


Effect  of  Fertilizers  on  Composition  of  Sweet 
Potatoes 


To  determine  the  effect  of  fertilizer  on  the  chemical 
composition  of  the  sweet  potato  at  harvesting,  Stuckey 
(93)  carried  out  the  experiments  as  indicated  in  Table 
12,  For  treatment  of  plats  i,  2,  3,  4,  5,  and  6,  see  p.  52. 


Drawing  Sprouts 


57 


Table  12 
Efect  oj  Fertilizer  on  Chemical  Composition 


1909 

Plat  I 

Plat  2 

Plat  3 

Plat  4 

Plats 

Plato 

Water 

65.72 
1.62 

0.39 
2.00 
1. 12 
5.46 
23.60 

65.83 
0.38 

i;i4 

5-50 
23-59 

64.32 
2.05 
0.41 
2.10 
1. 21 
6.25 

23.66 

66.81 

1-52 

0.37 
1.20 
1. 10 

5-75 
23-25 

69.10 
1.46 
0.36 
1. 10 
1. 00 
4.60 

22.38 

64.50 

Protein 

1-95 

Fat 

0.44 

Fiber 

2.10 

Ash 

1.20 

6.15 

Other  carbohydrates 

23-66 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

I9I0 


Plat  I 

Plat  2 

Plats 

Plat  4 

Plats 

Plat  6 

Water 

70.3 
1.5 
0.6 
4.1 
1.4 

22.1 

71.2 
1.4 
0.5 
3-8 
1.2 

21.9 

70.8 

1-5 
0.6 

3-9 

1-3 

21.9 

72.4 
1-3 
0.5 

3-2 

I.I 
21.5 

70.6 
1.6 
0.8 
3-1 
1-4 

22.5 

70.8 

1.7 

Fat 

0.8 

Crude  fiber 

3.0 

Ash 

1-3 

♦Carbohydrates. 

22.4 

100.00 

100.00 

100.00 

100 . 00 

100.00 

100.00 

♦Sugar 


;.o  I    7.6  I     8.2  I    8.5  I    9.1  I    8.9 


1911 


Plat  I 

Plat  2 

Plats 

Plat  4 

Plats 

Plat  6 

Water 

63-55 
1.70 
0-45 
5-45 
4.85 

21.63 
1. 00 
1-37 

65.30 
1.85 
0.50 
7-30 
6.25 

16.25 
1. 10 
1.45 

68.40 
1.30 
0.40 
6.20 
5.30 

15-25 

\& 

68.15 
1.20 
0.50 
5.15 
5.10 

17.13 
1-35 
1.42 

65-45 

o!48 
5.35 
5-15 
18.87 
1.75 
1.50 

66.20 

1-35 

Fat 

0.45 

Sucrose 

5.60 

Dextrine 

4-90 

Starch 

18.32 

Fiber 

1.80 

Ash 

1.35 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

Reduced  to  Dry  Basis 
Sucrose |  14.951  21.04I  19.621  16.17I  15.48I  16.56 


58 


The  Sweet  Potato 


Table  12 — (Contimied) 


1912 


Plat  I 


Plat  2 


Plat  3 


Plat  4 


Plats 


Plat  6 


Water 

Fat.. 

Protein 

Fiber 

Ash 

♦Carbohydrates 

*Sugar 


68.30 

0.34 
1.70 
2.10 
1. 19 
26.37 


65.92 
0.32 

1-75 

2.00 

1.30 

28.71 


68.75 
0.34 
1.65 
1-95 
1.30 

26.01 


69.40 
0.35 
1.60 
1.90 
115 

25.60 


70. 10 
0.36 

1-52 

1.85 

1. 10 

25.07 


68.30 
0.34 
1.72 
2.05 
1.28 

26.31 


100.00 


100.00 


100.00 


100.00 


100.00 


5-75 


5.10 


6.15 


6.05     4.90 


5.20 


1913 


Plat  I 

Plat  2 

Plat  3 

Plat  4 

Plats 

Plat  6 

Water 

60.02 
I. II 
0.18 
2.47 

21.00 
0.63 

60.46 
0.38 
0.21 
2.65 

21.66 
0.58 

66.24 
0.52 
0.31 
2.76 

23.90 
1-35 

72.65 

0.37 
0.17 
2.48 
19.22 
0.65 

71.50 
0.41 
0.18 
2.50 

0.64 

73.70 

Protein                  .      ... 

0.62 

Fat 

0.18 

2.24 

Starch 

18.09 

Crude  fiber 

0.71 

From  the  foregoing  table  it  is  seen  that  there  is  not 
sufficient  constancy  in  the  chemical  composition  of  the 
roots,  due  to  the  application  of  various  fertilizers  to 
justify  the  statement  that  chemical  composition  is 
affected  by  fertilizers.  However,  from  other  data  it 
seems  that  an  excess  of  nitrogen  produces  a  lighter  yel- 
low flesh,  with  an  insipid  flavor,  and  a  soggy,  soft 
texture  when  baked.  This  seems  to  be  the  case  espe- 
cially with  the  Pumpkin  Yam,  when  heavily  fertilized 
with  nitrate  of  soda.  However,  quality  seems  to  go 
hand  in  hand  with  applications  of  acid  phosphate,  or  a 
complete  fertilizer. 


Drawing  Sprouts  59 

Cultivation 

As  soon  as  the  plants  are  well  rooted,  cultivation 
should  begin.  It  is  poor  practice  to  allow  the  weeds  to 
get  the  best  of  the  grower.  A  few  days  after  planting, 
a  sweep  or  a  one-horse  plow  should  be  run  in  the  middle 
to  loosen  up  the  strip  of  earth  left  in  ridging.  AH  culti- 
vation should  be  of  a  shallow  nature,  and  this  is  espe- 
cially necessary  after  a  rain  or  irrigation.  As  far  as 
possible  all  cultivation  should  be  done  by  horse  and  culti- 
vator, and  the  hand  labor  reduced  to  one  or  two  hoeings. 
Some  soils  are  very  weedy  and  a  third  hand  hoeing  may 
be  necessary.  The  cost  of  hoeing  and  cultivation  has 
been  estimated  by  Garcia  (24)  in  New  Mexico  at  $5.60 
per  acre  during  the  season.  This  amount  will,  of 
course,  vary  in  different  states. 

A  two-horse  riding  cultivator  answers  in  the  cultiva- 
tion of  sweet  potatoes.  It  is  more  desirable  when  the 
cultivator  has  discs  instead  of  hoes,  as  it  can  also  be 
used  for  throwing  the  soil  towards  the  rows.  For  lay- 
ing by,  growers  frequently  use  a  single-row,  celery 
hiller,  or  a  one-horse  sweep  stock  which  can  be  fitted 
with  sloping  boards. ,  Some  growers  use  a  small  one- 
horse  turn  plow  for  the  final  cultivation,  going  twice  in 
each  alley  and  working  the  soil  toward  the  plants. 

Irrigation 

The  sweet  potato  can  stand  considerable  drought, 
however,  there  is  a  limit  beyond  which  it  will  actually 
burn  up.  Such  a  condition  was  experienced  in  many 
parts  of  Texas  during  the  summers  of  1917  and  1918. 
Wherever  possible,  irrigation  should  be  resorted  to  dur- 
ing prolonged  dry  spells.    In  New  Mexico,  especially  in 


6o  The  Sweet  Potato 

the  southern  part  of  the  state,  Irrigation  of  sweet 
potatoes  is  practiced  extensively.  It  is  not  uncommon 
there  to  give  six  to  ten  irrigations  during  the  season. 
In  New  Mexico,  Garcia  (24)  claims  that  when  the  sur- 
face soil  is  kept  moist  the  potatoes  are  not  formed  deep, 
but  are  made  nearer  to  the  surface  of  the  ground.  This 
is  also  true  in  other  states,  since  droughty  conditions 
force  the  roots  to  go  deep  for  their  moisture,  thus  mak- 
ing the  harvesting  very  difficult. 

Effect  of  Pinching  off  Vines 

In  case  of  heavy  vine  growth,  some  growers  make  it 
a  practice  to  cut  off  a  large  number  of  vines  in  order  to 
force  down  all  food  to  the  roots.  Frequently,  also, 
sweet  potato  vines  are  cut  back  and  fed  green  to  hogs. 
To  determine  the  effect  of  this  practice  on  the  final 
yield,  Stuckey  (93)  made  some  preliminary  tests.  In 
1912  six  rows  200  feet  long  were  well  fertilized  and 
planted  with  the  variety  Enormous,  early  in  May.  By 
June  14  the  vines  had  completely  covered  the  soil. 
Rows  I,  2,  5,  and  6  were  cut  back  to  one  foot  in  length, 
and  the  cut  vines  removed  from  the  field.  A  few  weeks 
later  these  had  grown  out  again  and  covered  the  soil. 
On  October  24th  the  potatoes  were  harvested  with  the 
results  as  seen  in  Table  13. 

Table  13 
Effect  oj  Cutting  Back  Vines  on  Yield 

Rows  I  and  2 680  pounds 

Rows  3  and  4 1062  pounds 

Rows  5  and  6 620  pounds 

From  Table  13  it  is  seen  that  cutting  back  the  vines 
reduces  the  yields. 


Drawing  Sprouts  6i 


Cost  of  Production, 

The  cost  of  producing  an  acre  of  sweet  potatoes  will, 
of  course,  depend  on  the  region  where  grown  and 
methods  of  culture.  Because  of  the  great  difference  in 
cost  of  labor,  rent  of  land,  cost  of  growing  plants,  fer- 
tilizers, storage,  and  marketing  facilities,  no  definite 
statement  can  be  made  to  hold  for  every  condition. 
Miller  (69)  gives  the  following  items  of  cost  of  pro- 
duction per  acre  in  some  of  the  eastern  sweet  potato 
sections : 

1.  Rent  of  land $  5.00 

2.  10,000  plants  at  $1.00  per  thousand. . ..     10.00 

3.  Fertilizer   15.00 

4.  Setting  plants  with  tongs  1.25 

5.  Cultivation    3.00 

6.  Harvesting  a  lOO-barrel  yield,  picking 

up  potatoes  at  15  cents  per  barrel. .      15.00 

7.  ICO  barrels  at  25  cents  each 25.00 

Total  cost  per  acre     $74.25 

This  does  not  Include  the  cost  of  hauling  to  market. 
In  some  parts  of  the  South  the  cost  of  producing  an 
acre  of  sweet  potatoes  will  not  exceed  $40.00  to  $50.00. 

The  average  price  received  for  sweet  potatoes  during 
1920  was  $2.50  to  $3.00  per  barrel.  At  this  rate 
$100.00  to  $200.00  is  often  realized  from  an  acre  of 
sweet  potatoes.  Success  with  sweet  potatoes  from  a 
financial  standpoint  depends  on  crop  rotation,  which  in- 
creases yield,  reduces  the  cost  of  fertilizer,  a;id  keeps 
down  disease.  Good  storage  houses,  and  a  knowledge 
of  the  best  marketing  conditions  will  also  help  to  make 
the  sweet  potato  crop  profitable. 


62 


The  Sweet  Potato 


Yield 

The  yield  per  acre  will  depend  on  the  season,  the 
amount  of  rainfall,  the  soil,  the  fertilizer  used,  the  time 
of  digging,  and  the  variety.  Varieties  which  are  best 
for  table  purposes,  seldom  produce  as  much  as  those 
which  are  less  desirable.  Although  it  is  not  uncommon 
to  obtain  yields  ranging  from  200  to  700  bushels  to  the 
acre,  yet  on  an  average,  200  bushels  per  acre  is  con- 
sidered satisfactory.  Varieties  grown  for  stock  food 
are  very  heavy  yielders.  Among  these  may  be  men- 
tioned the  Providence,  Hayman,  Norton,  Peabody,  Red 
Bermuda,  Shanghai,  Southern  Queen,  Nigger  Choker, 
and  Pumpkin  Yam. 

That  the  yield  is  influenced  by  the  time  of  digging 
was  shown  by  Stuckey  (93),  who  in  191 1  planted  the 
Golden  Beauty  and  Enormous.  These  were  harvested 
as  shown  in  Table  14. 

Table  14 
Yield  Affected  by  Time  of  Digging 


Variety 

Date 

of 

Harvest 

Yield 
Acre 

Price 

per 

Bushel 

Value 
Crop 

Golden  Beauty 

Golden  Beauty 

Sept.  II 
Nov.  II 
Sept.  II 
Nov.  II 

65.7bu. 
348.4  bu. 
177.2  bu. 
255- 8  bu. 

$1.25 
0.75 
1.25 
0.75 

$82,125 

261.30 

221.50 

191.85 

It  is  seen  that  early  digging  was,  in  the  case  of  Golden 
Beauty,  less  remunerative  than  late  digging,  although 
the  price  per  bushel  was  higher.  This  was  due  to  an 
enormous  loss  from  decrease  in  yield. 


CHAPTER  IV 

VARIETIES 

It  is  unfortunate  that  the  names  of  the  different  va- 
rieties of  sweet  potatoes  are  badly  confused.  The  same 
variety  may  have  many  names  under  different  growers 
and  in  various  localities.  The  variety  "Big  Stem  Jer- 
sey," for  instance,  parades  under  fifty  names  in  some 
of  the  sweet  potato  states.  Growers  seem  to  vie  with 
each  other  as  to  who  will  present  to  the  buyer  of  plants 
more  new  varieties  (really  old  varieties  with  changed 
names).  The  same  confusion  exists  in  the  literature. 
Horticulturists  in  the  various  Experiment  Stations  have 
been  slow  to  develop  a  system  of  classifying  sweet  pota- 
toes. The  common  variety,  Southern  Queen,  has  been 
so  variously  described  by  different  workers,  that  it  leads 
one  to  believe  that  few  of  the  workers  dealt  with  that 
variety. 

The  sweet  potato  constitutes  a  staple  food  crop. 
Before  any  headway  may  be  made  on  the  breeding  and 
improvement  of  this  crop  it  is  essential  to  devise  a  uni- 
form system  of  classification,  so  as  to  standardize  all 
varieties  and  eliminate  all  the  confusion  in  nomen- 
clature. 

Price  (78  J  was  the  first  to  devise  a  system  of  classi- 
fication based  on  the  shape  of  the  leaves,  which  is  as 
follows : 

a.  Foliage  Round  or  Entire.  This  includes  the  Up 
63 


64  The  Sweet  Potato 

River,  Big  Stem  Jersey,  Pumpkin,  Shanghai,  Norton, 
Hayman,  and  Southern  Queen. 

b.  Foliage  Shouldered.  This  includes  the  Gold  Skin, 
Delaware,  Extra  Early,  Caroline,  Early  Golden,  Yellow 
Jersey,  Brazilian,  Red  Bermuda,  Red  Nose,  New  Jersey, 
Yellow  Nansemond,  Negro  Choker,  Red  Nansemond, 
Red  Bermuda,  and  Peabody. 

c.  Foliage  Lobed.  This  includes  Barbados,  Sugar 
(Creole),  Yellow  Yam,  Vineless  (Bunch  Yam,  Early 
Bunch  Yam),  Spanish  Yam,  Georgia,  and  Tennessee. 

In  the  United  States  few  workers  seem  to  have 
adopted  Price's  system  of  classification.  However,  this 
system  was  adopted  by  Robson  (84)  in  his  description 
of  West  Indian  varieties. 

A  key,  based  on  shape  of  foliage  alone,  is  very  inade- 
quate. The  same  vine  will  often  have  half  a  dozen 
variously  shaped  leaves.  To  classify  sweet  potatoes  as 
to  shape,  size,  color,  or  quality  of  tuber  is  also  a  hope- 
less task. 

In  the  adoption  of  a  key,  the  distinguishing  charac- 
ters must  be  reasonably  permanent.  The  abundance  of 
latex  and  the  color  of  leaves  in  sweet  potatoes  are  not 
constant  enough  to  be  reliable.  It  is  to  the  credit  of  Dr. 
Groth  (26)  to  have  worked  out  the  best  key  so  far 
known ;  hence  it  is  adopted  by  the  author  because  of  the 
following  reasons : 

I.  It  is  a  key  and  a  classification  combined.  All  va- 
rieties are  determined  by  the  same  characters  and  can 
be  readily  compared,  while  in  the  ordinary  key  each 
variety  is  thrown  out  at  an  opportune  moment  by  a  char- 
acter which  may  be  common  to  many  others  already 
separated  by  some  other  character.  One  comes  to  asso- 
ciate that  particular  character  with  that  variety,  while 
in  reality  it  depends  entirely  on  the  arbitrary  arrange- 


Varieties  65 

ment  of  the  key  whether  the  character  is  used  at  all. 
Similarly  there  is  very  little  attempt  made  in  the  ar- 
rangement of  the  ordinary  key  to  keep  together  the  va- 
rieties, resembling  each  other,  while  in  this  key  they 
stand  together  naturally.  For  example.  Bronze  Spanish, 
as  the  name  indicates,  has  a  peculiarly  colored  tuber.  In 
the  ordinary  key  this  character  would  very  probably  be 
used  at  an  earlier  stage  to  separate  it.  Black  Spanish 
has  a  tuber  which  is  similar  to  several  others,  and  it 
would  be  hard  to  separate  it  by  that  character.  Yet  the 
two  can  not  be  told  apart  in  the  field,  unless  one  digs  for 
the  tubers. 

2.  It  can  be  used  with  incomplete  specimens.  If  a  cer- 
tain character  can  not  be  determined  from  the  material 
on  hand,  the  space  reserved  for  it  may  be  left  blank, 
and  the  next  character  taken  up.  One  is  not  continually 
before  alternatives  which  may  be  at  the  time  unanswer- 
able. It  is  likely  that  the  determination  is  possible  even 
without  that  character. 

3.  It  is  more  convenient  to  the  non-scientist.  In  the 
determination  of  all  varieties  the  same  process  is  gone 
through,  and  once  that  process  is  learned  by  heart  it 
need  not  be  changed  again  for  the  determination  of  the 
next  variety. 

4.  It  is  flexible.  The  writer  is  certain  that  he  has  not 
studied  all  varieties  existing.  New  varieties  can  be 
easily  catalogued  and  inserted  in  the  list  by  any  one.  In 
the  ordinary  key  the  advent  of  a  variety  necessarily 
causes  confusion,  as  it  not  only  could  be  wrongly  de- 
termined, but  would  also  interfere  with  the  determina- 
tion of  other  varieties  which  might  agree  with  it  in  the 
critical  characters.  This  would  make  an  ordinary  key 
useless,  while  this  key  provides  for  all.  Should  other 
characters  be  found  which  would  aid  in  the  determina- 


66  The  Sweet  Potato 

tion,  they  could  simply  be  entered  under  subsequent 
letters  L,  M,  N,  etc.,  without  interfering  in  the  least 
with  the  working  of  the  key. 

Groth's  Key  for  Classifying  Sweet  Potatoes 

^',  Shape  of  leaf. 

1.  Cut. 

2.  Round. 

3.  Long. 

4.  Broad. 

5.  Mixed  (round  and  lobed)'. 

B.  Size  of  leaf. 

1.  Small  (less  than  4  inches  across). 

2.  Large  (more  than  4  inches  across). 

C.  Length  of  stem. 

1.  Long  (more  than  4  feet  long). 

2.  Short  (less  than  4  feet  long), 

D.  Color  of  stem. 

1.  Green  (with  or  without  brownish  areas). 

2.  Green,  with  purple  around  the  axils  of  the  leaves. 

3.  Greenish-brown  to  purple. 

4.  Purple. 

E.  Size  of  stem. 

1.  Thin  (less  than  5^  inch  in  diameter). 

2.  Thick  (more  than  ^  inch  in  diameter,  often  3-16 

or  more). 

F.  Presence  of  star. 

1.  Star  present 

2.  Star  absent. 

G.  Color  of  lower  surface  of  veins. 

1.  Veins  purple. 

2.  Midrib  pinkish  in  some  old  leaves. 

3.  Purple  spot  at  the  base  of  the  midrib. 

4.  Veins  all  green. 

H.  Arrangement  of  hair  on  upper  surface  of  leaf. 
I.  Hair  all  over. 


Varieties  67 

2.  Chiefly  on  tip  and  along  veins. 

3.  Absent. 

/.  Outside  color  of  tubers. 

1.  White. 

2.  Yellow,  golden  or  bronze. 

3.  Yellow-red  or  pinkish. 

4.  Red  or  purple. 

/.  Color  of  the  flesh  of  the  tubers. 

1.  White. 

2.  Cream-colored  or  yellowish-white. 

3.  Pinkish-white  or  pinkish-yellow. 

4.  Pink-orange. 

5.  Marked  with  purple. 

K.  Distinctness  of  wood  elements  in  tuber. 

1.  Distinct. 

2.  Blurred. 

3.  Not  visible. 

How  TO  Use  the  Key 

The  use  of  the  key  is  very  simple.  Take  an  unknown 
plant  or  one  that  is  parading  under  a  false  name  to  be 
determined.  Let  us  suppose  that  its  leaves  are  cut.  This 
will  put  it  in  Ai.  The  majority  of  the  full-grown 
leaves  are  more  than  4  inches  across  from  tip  to  tip  of 
the  most  spreading  lobes.  This  will  bring  it  in  B2. 
Suppose  the  full-grown  stems  are  shorter  than  four  feet. 
This  will  put  It  in  C2.  As  the  stems  are  green  with 
purple  marks  around  the  axil  of  the  leaves,  we  have 
D2.  The  full-grown  stems  measure  3/16  of  an  inch  at 
their  thickest  point — a  characteristic  indicated  by  E2. 
The  purple  star  is  clear  and  the  lower  surface  of  the  vein 
is  purple — characteristics  indicated  by  Fi  and  Gi.  As  a 
few  of  the  younger  leaves  show  a  few  scattered  hairs  on 
the  midrib,  and  some  of  the  older  leaves  have  no  hair  at 
all,  we  express  these  facts  by  H2,  3.  The  roots  we  find  to 


68  The  Sweet  Potato 

be  white  outside  and  inside,  which  means  1 1  and  Ji. 
The  bundles,  or  wood  elements,  are  not  visible  on  the 
freshly  cut  surface.  This  fact  is  indicated  by  K3.  Thus 
our  formula  runs:  Ai,  B2,  C2,  D2,  E2,  Fi,  Gi,  H2,  3, 
Ii,  Ji,  K3.  When  we  refer  to  the  alphabetical  arrange- 
ment of  the  formulas,  we  find  that  it  Is  the  formula  of 
Ticotea.  If  all  these  points  agree,  we  may  be  certain 
that  the  variety  is  Ticotea. 

Latest  Method  of  Classification 

Perhaps  the  latest  and  most  recent  method  of  classi- 
fying sweet  potatoes  is  that  of  Thompson,*  who  places 
all  varieties  in  eight  groups.  A  key  to  these  groups 
follows: 

KEY  TO  THE  GROUPS 

I.  Leaves  deeply  lobed  or  parted — i  and  2. 
(i)  Leaves  with  purple  stain  at  the  base  of  the  leaf  blades. 

Ticotea. 
(2)  Leaves  without  purple  stain  at  the  base  of  the  leaf  blades. 

Belmont. 
II.  Leaves  not  deeply  lobed  or  parted — i  and  2. 

(i)  Leaves  with  purple  stain  at  the  base  of  the  leaf  blades — A 
and  B. 
{A)  Stems  purple  or  greenish  with  decided  tinge. . .  .Spanish. 
(B)  Stems — o  and  6. 

(o)  Leaves  entirely  to  slightly  shouldered;  roots  white. 

Shanghai. 
(6)  Leaves  toothed  with  6  to  lo  low  marginal  teeth,  or 
entire;  roots  salmon  or  yellow  tinged  with  salmon. 

Florida. 
(2)  Leaves  without  purple  stain  at  the  base  of  the  blade  or  with 
very  faint  stain — A  and  B. 

{A)  Stems  purple Southern  Queen. 

(5)  Stems  green — a  and  h. 

(a)  Stems  medium  to  large  in  size;  roots  fusiform,  yellow 

tinged  with  salmon,  with  light  yellow  veins  Pumpkin. 

(6)  Stem  slender;   roots  russet  yellow  or  red,  ovoid  to 

fusiform Jersey 

*  Thompson,  J.  C,  and  Beattie,  J.  H.  "Group  classification  and 
varietal  descriptions  of  American  varieties  of  sweet  potatoes."  TJ.  S. 
Dept.  oj  Agr.  Bui.  No.  1021:  1-30,  1922.     {With  bibliography.) 


Varieties 


69 


The  classification  of  the  varieties  in  the  eight  groups 
is  as  follows: 


Group 


TiCOTEA 


Belmont 


Belmont 
Bunchsection 


Spanish 
Yellow  Span- 
i.sh  section 

Spanish 
Bermuda  sec 

Hon 
Spanish 
Red  Spanish 

section 


Varieties  Belonging  to  the  Group 


Ticotea,  Koali 


Belmont,  Eclipse  Sugar  Yam,  Vineless  Pumpkin  Yam, 

Old  Time  Yam,  Yellow  Yam,  and  White  Scaly 
Gros  Grandia,  Bunch  Candy  Yam 


Shanghai 


Florida 


Southern 
Queen 


Pumpkin 


Jersey 

Red  Jersey 
section 

Jersey 

Big  stem  Jer- 
sey section 

Jersey 

Yellow  Jersey 
section 


Pierson,  Yellow  Strasburg,  Yellow  Spanish,  Triumph 


Red  Bermuda,  Red  Brazil,  Porto  Rico,  Key  West  Yam. 
Creola 

Red  Spanish,  Purple  Yam,  or  Nigger  Choker,  Dahomey 


Shanghai,  Minnet  Yam 


Florida,  General  Grant,  Vineless,  Nancy  Hall 


White  Yam,  Southern  Queen 


Pumpkin  Yam,  Norton,  Dooley,  White  Gilke 


Japan  Brown,  Red  Jersey 
Big  Stem  Jersey,  Philipili 
Yellow  Jersey,  Gold  Skin 


CHAPTER  V 

HARVESTING 

When  sweet  potatoes  are  dug  for  early  market,  ma- 
turity is  no  consideration.  In  this  case  the  roots  are 
dug  just  as  soon  as  they  are  of  marketable  size.  For 
this  purpose,  it  is  more  economical  to  plant  a  definite 
acreage  in  early-maturing  varieties  that  will  be  ready  to 
be  dug  in  August.  For  storage  purpose,  however,  the 
crop  must  be  harvested  when  it  is  well  matured.  Im- 
mature roots  are  very  hard  to  keep.  However,  few 
agree  as  to  what  constitutes  maturity.  It  is  believed  that 
a  fully  mature  potato,  when  cut  open,  will  soon  dry  and 
form  a  white  hard  crust  on  the  cut  surface,  while  an  im- 
mature potato  will  bleed,  and  the  cut  surface  will  remain 
moist,  thereby  inviting  the  entrance  of  the  germs  which 
produce  rots.  Climate,  rainfall,  favorable  growing  sea- 
son, soil,  fertilizer,  and  variety  used  are  all  factors 
which  influence  early  or  late  maturity.  The  tendency  is 
to  dig  as  late  as  possible,  so  as  to  increase  the  yield. 
This  is  safe  enough  in  a  comparatively  dry  fall.  Dur- 
ing excessive  rainfall,  which  may  occur  late  in  the  sea- 
son, extra  growth,  although  increasing  the  yield,  will  not 
be  conducive  to  good  keeping.  Rapid  growth  before 
digging  means  roots  gorged  with  moisture,  and  uneven 
development,  which  results  in  cracking  of  the  matured 
roots.  Sweet  potatoes  are  very  sensitive  to  cold.  A 
light  frost,  when  only  slightly  injuring  the  vines,  may 
70 


Harvesting  71 

not  hurt  the  roots ;  however,  a  heavy  frost  becomes  dan- 
gerous. When  the  vines  are  killed  by  frost  they  should 
at  once  be  cut  off  and  the  roots  dug  immediately.  When 
the  frost  is  very  severe,  and  penetrates  the  tip  ends  of 
the  potatoes,  no  attempt  should  be  made  to  store  them. 
Frost  injured  potatoes  are  poor  keepers.  They  can  be 
saved  if  disposed  of  for  early  consumption. 

The  ideal  time  to  dig  is  during  dry  warm  weather. 
Digging  during  wet  spells  should  be  avoided,  as  at  that 
time  bruising  the  potatoes  in  the  field  will  encourage  far 
more  rapid  rotting.  Furthermore,  during  such  weather 
the  potatoes  will  naturally  be  more  watery,  and  hence 
will  require  longer  curing.  If  the  season  should  be  too 
wet  and  the  grower  is  forced  to  dig,  the  potatoes  will  be 
put  in  the  house  wet  and  muddy.  When  such  con- 
ditions prevail,  the  potatoes  must  be  dried  quickly.  Such 
wet  potatoes  should  not  be  stored  in  great  bulk,  but 
rather  in  various  bins,  in  small  quantities,  or  possibly 
they  should  be  left  in  the  hampers  and  kept  for  at  least 
twenty-four  hours  in  a  dry  shed,  where  the  excessive 
moisture  will  have  a  chance  to  evaporate.  It  is  not  a 
good  practice  to  dig  the  potatoes  late  in  the  evening  and 
allow  them  to  remain  uncovered  during  the  night,  as 
they  may  be  greatly  injured  by  frost  or  by  rain.  Neither 
is  it  advisable  to  dig  very  early  in  the  morning,  when 
the  ground  is  more  or  less  cool  and  the  vines  damp  with 
dew.  The  best  time  to  dig  is  after  the  sun  is  well  up 
and  until  3  or  4  in  the  afternoon,  or  only  until  such  time 
that  the  grower  will  be  able  to  pick  up  all  that  he  has 
dug  that  day.  It  is  never  advisable  to  allow  the  dug 
potatoes  to  remain  exposed  too  long  to  the  sun,  although 
a  few  hours'  exposure,  when  the  outdoor  temperature  is 
75  to  80  degrees  F.,  will  be  beneficial,  as  it  will  help  to 
dry  the  roots.    Should  the  weather  be  very  hot,  too  long 


72  The  Sweet  Potato 

exposure  to  the  sun  will  blister  the  potatoes  and  cause 
them  to  rot  in  storage. 

The  investigations  of  Hasselbring  (54  and  55)  shed 
considerable  light  on  the  question  of  maturity  in  regard 
to  harvesting.  It  is  evident  that  marked  changes  occur 
in  the  roots  the  latter  part  of  the  season ;  hence  the  time 
of  harvesting  will  largely  depend  on  the  purpose  for 
which  the  sweet  potatoes  are  intended,  namely,  stock 
feed,  silage,  or  the  manufacture  of  starch.  In  the  latter 
case,  harvesting  should  be  done  when  the  starch  con- 
tent is  at  its  maximum.  According  to  Hasselbring,  the 
composition  of  the  roots  during  the  latter  part  of  the 
growing  season  seems  to  remain  remarkably  uniform, 
presenting  no  striking  or  irregular  fluctuations.  At  this 
time  the  roots  in  the  soil  contain  their  maximum  amount 
of  starch  with  the  minimum  amount  of  sugar.  As  soon 
as  the  vines  begin  to  dry,  water  immediately  accumu- 
lates in  the  roots  as  a  result  of  cessation  of  transpi- 
ration. Because  of  the  destruction  of  leaves  the  trans- 
formation of  carbohydrates,  that  is,  the  change  of  starch 
into  sugar,  which  is  so  characteristic  of  sweet  potatoes 
in  storage,  begins  to  take  place  in  the  field.  Reducing 
sugar  is  formed  first  as  an  intermediate  step  in  the 
change  from  starch  to  cane  sugar.  It  is  evident  from 
this,  that  on  no  account  should  harvesting  of  sweet  pota- 
toes be  delayed  after  the  leaves  have  been  killed  by 
frost. 

Implements  for  Harvesting 

On  small  areas,  and  for  home  use,  sweet  potatoes  may 
be  dug  with  a  spading  fork.  On  a  large  scale,  plows 
designed  for  that  purpose  are  used.  In  eastern  Virginia, 
a  vine  cutter  is  run  over  the  rows  in  order  to  cut  the 
vines  first,  and  the  roots  are  then  thrown  out  with  an 


Harvesting  73 

ordinary  turning  plow.  This  system  is  not  satisfactory, 
as  the  turn  plow  bruises  the  roots.  Frequently  an  or- 
dinary disc  harrow  is  used  to  cut  the  vines,  and  all  but 
two  of  the  discs  are  removed.  Such  an  arrangement 
works  well  in  cutting  off  the  vines.  However,  the  discs 
often  sink  deep  in  the  soil,  and  bruise  the  roots.  Ma- 
chines used  for  digging  Irish  potatoes  are  not  suitable 
for  harvesting  sweet  potatoes,  as  they  bruise  and  other- 
wise injure  them.  A  good  type  of  digger  is  a  plow  with 
rolling  coulters  on  the  beam  to  cut  the  vines,  and  with 
rods  attached  to  the  moldboard  to  free  the  roots  from 
the  soil  and  vines.  Another  type  of  digger  is  also  shown 
in  Fig.  ic.  Both  these  kinds  of  plows  loosen  the  hills 
of  potatoes  without  disturbing  the  ground  around  them. 
The  potatoes  then  must  be  scratched  out.  This  is  done  by 
taking  hold  of  the  stem  end  of  the  hill  and  firmly  pull- 
ing the  roots  which  cling  to  the  main  stem  out  of  the 
soil.  A  small  jerk  and  shake  will  detach  and  free  all 
the  potatoes  from  that  hill.  Here  care  is  necessary  since 
careless  helpers  will  often  use  force  in  shaking  the  hill 
and  thus  violently  throw  the  roots  on  the  ground  and 
bruise  them  badly.  To  facilitate  grading  in  the  field 
and  filling  the  hampers,  potatoes  from  three  to  four 
rows  are  placed  together.  This  is  easily  done  when 
four  "scratchers"  are  instructed  to  put  their  potatoes 
in  one  row.  Potatoes  once  gathered  in  the  hampers  or 
containers  should  not  be  allowed  to  remain  exposed  in 
the  field  because  of  danger  of  overheating.  Overheated 
potatoes  will  not  cool  off  so  rapidly  in  storage  and  hence 
will  rot  before  early  curing  is  completed. 

Finally,  during  digging,  scratching,  and  grading, 
every  reasonable  precaution  should  be  taken  to  avoid 
bruising  the  sweet  potatoes.  It  is  true  that  many  bruised 
potatoes  keep  well  and  do  not  rot,  but  it  is  equally  true 


74  The  Sweet  Potato 

that  a  large  percentage  of  the  rotting  begins  at  the  place 
of  a  cut  or  bruise.  Frequently  wounded  sweet  potatoes 
heal  over  by  forming  a  layer  of  starch  free  cells  beneath 
the  injured  surface.  This  naturally  tends  to  ward  off 
infection.  Weimer  (112)  has  found  that  wounds  heal 
over  under  storage  conditions  of  33  degrees  C.  and  a 
relatively  high  humidity. 

Grading 

Sweet  potatoes  are  generally  sorted  into  two  grades, 
primes  and  culls.  These  grades  are  based  on  size;  all 
culls  include  the  small  and  stringy  potatoes.  Frequently 
a  third  grade  or  "extra  prime"  is  made,  and  this  con- 
sists of  extra  choice  potatoes,  uniform  in  size,  regular 
in  shape  and  free  from  cracks  and  diseased  spots.  Fin- 
ally a  fourth  grade  is  often  made,  which  includes  all  the 
extra  large  ones  or  "Jumbos." 

To  save  time  and  labor,  it  is  best  to  grade  in  the  field 
during  harvesting.  A  desirable  plan  is  to  go  over  the 
rows  and  pick  up  all  seed  potatoes  first,  then  the  mar- 
ketable roots,  and  finally  all  bruised  ones  and  culls, 
which  are  stored  separately  or  used  for  stock  feed.  The 
following  are  the  grades  suggested  by  the  United  States 
Department  of  Agriculture,  Bureau  of  Markets,  Depart- 
ment Circular  99,  1920: 

United  States  Grades  for  Sweet  Potatoes 

U.  S.  Grade  No.  i 

U.  S.  Grade  No.  i  shall  consist  of  sound  sweet 
potatoes  of  similar  varietal  characteristics  which 
are  practically  free  from  dirt  or  other  foreign  mat- 


Harvesting  75 

ter,  frost  injury,  decay,  bruises,  cuts,  scars,  cracks, 
and  damage  caused  by  heat,  disease,  insects  (in- 
cluding weevils),  or  mechanical  or  other  means. 

The  diameter  of  each  sweet  potato  shall  i^ot  be 
less  than  one  and  three-quarter  inches  nor  more  than 
three  and  one-half  inches,  and  the  length  shall  not 
be  less  than  four  inches  nor  more  than  ten  inches, 
but  the  length  may  be  less  than  four  inches  if  the 
diameter  is  two  and  one-quarter  inches  or  more. 

In  order  to  allow  for  variations  incident  to  com- 
mercial grading  and  handling,  five  per  cent,  by 
weight,  of  any  lot  may  not  meet  the  requirements 
as  to  diameter  and  length,  and,  in  addition,  six  per 
cent,  by  weight,  may  be  below  the  remaining  re- 
quirements of  the  grade. 

Any  lot  in  which  the  diameter  is  not  less  than  one 
and  one-half  inches  and  which  contains  a  greater 
percentage  by  weight  of  sweet  potatoes  below  one 
and  three-quarters  inches  than  is  permitted  in  U.  S. 
Grade  No.  i,  but  which  otherwise  meets  the  re- 
quirements of  such  grade  shall  be  designated  as 
U.  S.  Grade  No.  i  Medium. 

'Any  lot  in  which  the  length  is  not  less  than  six 
inches  nor  more  than  twelve  inches  and  which 
contains  a  greater  percentage  by  weight  of  sweet 
potatoes  above  ten  inches  in  length  than  is  per- 
mitted in  U.  S.  Grade  No.  i,  but  which  otherwise 
meets  the  requirements  of  such  grade  shall  be  desig- 
nated as  U.  S.  Grade  No.  i  Long. 


U.  S.  Grade  No.  2 

U.  S.  Grade  No.  2  shall  consist  of  sound  sweet 
potatoes  of  similar  varietal  characteristics,  not 
meeting  the  requirements  of  the  foregoing  grades, 
which  are  free  from  serious  damage  caused  by  dirt 
or  other  foreign  matter,  frost  injury,  decay,  bruises, 


76  The  Sweet  Potato 

cuts,  scars,  cracks,  heat,  disease,  insects,  or  me- 
chanical or  other  means,  and  which  are  not  less 
than  one  and  one-half  inches  nor  more  than  three 
and  one-half  inches  in  diameter. 

In  order  to  allow  for  variations  incident  to  com- 
mercial grading  and  handling,  five  per  cent  by- 
weight  of  any  lot  may  not  meet  the  requirements  as 
to  diameter,  and,  in  addition,  six  per  cent  by  weight 
may  be  below  the  remaining  requirements  of  this 
grade. 

U.  S.  Jumbo  Grade 

U.  S.  Jumbo  Grade  shall  consist  of  sound  sweet 
potatoes  of  similar  varietal  characteristics,  which 
are  free  from  serious  damage  caused  by  dirt  or  other 
foreign  matter,  frost  injury,  decay,  bruises,  cuts, 
scars,  cracks,  heat,  disease,  insects,  or  mechanical 
or  other  means,  and  which  are  not  less  than  three 
and  one-half  inches  in  diameter. 

In  order  to  allow  for  variations  incident  to  com- 
mercial grading  and  handling,  five  per  cent  by 
weight  of  any  lot  may  be  less  than  the  diameter 
prescribed,  and,  in  addition,  six  per  cent  by  weight 
may  be  below  the  remaining  requirements  of  this 
grade. 

U.  S.  Grade  No.  3 

U.  S.  Grade  No.  3  shall  consist  of  sweet  potatoes 
not  meeting  the  requirements  of  any  of  the  fore- 
going grades. 

Definition  of  Grade  Terms  as  Used  in  These  Grades 

"Practically  free"  means  that  the  appearance 
shall  not  be  injured  to  an  extent  readily  apparent 
upon  casual  examination  of  the  lot,  and  that  any 
damage  from  the  causes  mentioned  can  be  removed 


Harvesting  77 

without  appreciable  increase  in  waste  over  that 
which  would  occur  if  the  sweet  potatoes  were  per- 
fect. 

"Diameter"  means  the  greatest  dimension  at 
right  angles  to  any  portion  of  a  central  line  run- 
ning through  the  sweet  potato  from  stem  end  to 
root  end. 

"Free  from  serious  damage"  means  that  any 
damage  from  the  caused  mentioned  can  be  removed 
without  increase  in  waste  of  more  than  ten  per  cent 
by  weight  over  that  which  would  occur  if  the  sweet 
potatoes  were  perfect. 

Hauling 

After  the  potatoes  have  been  properly  graded  and 
either  crated  or  placed  in  hampers  they  should  be 
hauled  to  the  storage  house.  The  containers  should  be 
filled  full  and  tightly  covered  to  prevent  jolting.  They 
should  then  be  placed  on  a  spring  wagon  and  the 
smoothest  road  preferred  for  hatiling.  'This  is  done  to 
prevent  every  unnecessary  jar.  If  a  spring  wagon  is 
not  available,  the  jarring  may  be  overcome  to  a  certain 
degree  by  placing  a  good  layer  of  hay  or  straw  on  the 
bottom  of  the  wagon.  There  are  also  springs  made  for 
temporary  insertion  in  farm  wagons. 

Whenever  possible,  the  storage  house  should  be  situ- 
ated near  the  center  of  production,  to  shorten  the  haul 
and  cause  less  damage  to  the  potatoes.  On  no  occasion 
should  potatoes  be  dumped  into  the  wagon  and  carried 
to  the  house.  Neither  should  they  be  filled  into  sacks 
and  laid  on  the  wagon  to  be  taken  to  storage.  It  is 
very  common  for  growers  to  ship  several  carloads  or 
sometimes  their  entire  crop  to  some  far  distant  town  to 
be  stored.    This  is  permissible  if  the  purchaser  know- 


78  The  Sweet  Potato 

ingly  buys  such  a  product,  for  he  takes  the  risk  of  losing 
a  large  part  of  the  crop  from  rots.  For  best  results  and 
economy,  sweet  potatoes  should  never  be  shipped  long 
distances  by  rail  or  water,  for  storage.  Under  these 
circumstances  it  is  safer  to  sell  the  crop  early  than  to 
attempt  to  store  it.  The  best  practice  requires  building 
a  storage  house  at  the  time  the  acreage  is  decided  upon. 


CHAPTER  VI 

USES  OF  THE  SWEET  POTATO 

The  sweet  potato,  if  properly  developed,  can  be  util- 
ized commercially  in  more  than  one  way. 

As  A  Food 

In  the  South  the  sweet  potato  is  depended  upon  as 
one  of  the  staple  crops.  In  the  Northern,  Eastern,  and 
iWestern  states  its  edible  qualities  are  being  recognized 
more  and  more.  In  the  South,  under  ordinary  cropping 
systems,  corn  usually  yields  twenty  bushels  per   acre. 

Table  15 

Analyses  of  Various  Feeding  Stuffs  Compared  with  the 
Sweet  Potato 


Per 
Cent. 
Water 


Per 
Cent. 
Ash 


Per 

Cent. 
Protein 


Per 

Cent. 
Crude 
Fiber 


Per 

Cent 
Nitrogen 

Free 
Extract 


Per 

Cent. 

Ether 

Extract 


Irish  potato 

Beets,  common 

Turnips 

Ruta-bagas 

Carrots 

Parsnips 

Artichokes 

Sweet  potato.. 
Com 


78.9 
88.5 
90.5 
88.6 
88.6 
88.3 

79-5 
68.1 
10.6 


i.o 
i.o 
0.8 
1.2 
1.0 
0.7 
1.0 
1.0 
1-5 


2.1 
1-5 
I.I 
1.2 
I.I 
1.6 
2.6 
1.6 
10.3 


0.6 
0.9 
1.2 
1-3 
1-3 
1.0 
0.8 
0.9 
2.2 


173 
8.0 
6.2 

7-5 
7.6 
10.2 
159 
27.9 
70.4 


O.I 

0.1 
0.2 
0.2 
0.4 
0.2 
0.2 
0.5 
50 


79 


8o 


The  Sweet  Potato 


With  sweet  potatoes  the  yields  vary  from  one  hundred 
to  two  hundred  bushels  per  acre,  furnishing  nearly  three 
times  the  food  value  corn  does.  Tables  15  and  16  by 
Keitt  (58)  compare  the  feeding  value  of  various  vege- 
table crops  with  that  of  the  sweet  potato. 

Table  16 

Yield  and  Feeding  Stuff  Analyses  of  the  Different  Varieties 
of  Sweet  Potatoes 


Variety 

Yield 
Bushels 

Per 
Cent. 
Water 

Per 

Cent. 

Protein 

Per 
Cent. 
Fat 

Per 

Cent. 

Fiber 

Per 

Cent. 

Ash 

Per 
Cent. 

Nitro- 
gen 
Free 

Extract 

Nancy  Hall 

Polo. 

270.0 
281.0 
416.0 
141. 0 
191. 0 
450.0 
158.0 
281.0 
214.0 
180.0 

270.0 
1740 
141.0 
326.0 

68.75 
72.53 
68.38 
67.27 
66.52 

65.45 
72.80 
68.87 
72.12 
65.67 

62.20 
65.82 
69.84 
67.74 

1.75 

1-52 

\it 

1.66 
1.50 
1-33 
1.83 

2.18 
1. 15 
1-45 
1.77 

0.60 
0.33 
0.47 

0.45 
0.74 
0.56 
0.49 
0.51 
0.50 
0.33 

0.65 

0.31 
0.50 

0.37 

1. 00 
0.78 
0.74 
0.73 
0.82 

1. 00 
0.96 
1.05 
1.09 

1. 01 

0.97 
0.66 
0.73 
0.79 

0.89 
1.09 
1.08 
0.89 
0.79 

1. 10 
1.09 
1.04 
1. 00 
1. 19 

1. 11 

0.82 
0.70 
0.83 

27.01 
23.75 

Southern  Queen. . . . 

White  Spanish 

General  Grant 

27.81 
29.18 
29.79 
30.24 

Arkansas  Beauty.  .  . 
Tennessee  Notchleaf 
Yellow  Nancemond. 

Purple  Yam 

Pumpkin  Early  Yel- 
low Yam 

Shanghor  Yam 

Vineland  Bunch  Yam 
Fulleton  Yellow  Yam 

23.00 
27.03 
23.96 
29.97 

32.89 
31  24 
26.78 
28.50 

Average 

250.0 

68.1 

1.6 

0.5 

0.9 

I.O 

27.9 

In  general  the  chemical  composition  of  sweet  pota- 
toes resembles  that  of  the  Irish  potato.  The  former, 
however,  contains  on  an  average  about  9  per  cent  less 
water  and  9  per  cent  more  carbohydrates  than  the  Irish 
potato.  This  is  shown  in  Table  1 7  by  Langworthy .  (  59) . 


Uses  of  the  Sweet  Potato 


8i 


Table  17 

Average  Chemical  Composition  of  Sweet  and  Irish  Potatoes 


Refuse 

Water 

Pro- 
tein 

Fat 

Carbohydrates 

Ash 

Fule 

Kind  of 
Potato 

Sugar, 

Starch, 

etc. 

Crude 
Fiber 

Value 

per 

Pound 

Sweet      potato 
(edible     por- 
tion) 

Per 

Cent. 

Per 

Cent. 

69.0 

Per 
Cent. 

1.8 

Per 

Cent. 

0.7 

Per 
Cent. 

26.1 

Per 

Cent. 

1-3 

Per 
Cent. 

I.I 

Calo- 
ories 

560 

Sweet       potato 
(as  purchased) 

20.0 

55.2 

1.4 

0.6 

21.0 

0.9 

450 

Sweet       potato 
(cooked) 

.... 

51-9 

30 

2.1 

42.1 

0.9 

905 

Sweet      potato 
(canned) 

.... 

55-2 

1-9 

0.4 

40.6 

0.8 

I.I 

800 

White  potato  for 
comparison 
(edible       por- 
tion) 

78.3 

2.2 

o.i 

18.0 

0.4 

I.O 

375 

White  potato  for 
comparison 
(as  purchased) 

20.0 

62.6 

1.8 

o.i 

14-7 

0.8 

305 

Although  containing  less  protein  than  the  Irish  potato, 
the  sweet  potato  has  a  larger  proportion  of  available 
protein,  estimated  at  about  13  per  cent.  The  proportion 
of  sugar  and  starch  varies  with  the  varieties.  Those 
grown  in  New  Jersey,  Maryland,  and  Delaware,  for  in- 
stance, are  rich  in  starch.  The  Southern  varieties  on 
the  other  hand  contain  a  larger  per  cent  of  sugar.    The 


82  The  Sweet  Potato 

proportion  of  total  sweet  potato  discarded  with  the  skin 
as  waste  is  about  20  per  cent,  the  same  as  for  the  Irish 
potato. 

Cooking  Recipes 

The  reason  sweet  potatoes  are  not  more  generally 
used  is  that  few  people  except  perhaps  those  in  the 
South  know  how  to  cook  them.  Sweet  potatoes  can  be 
prepared  in  more  than  one  way  and  indeed  our  liking 
for  this  delicious  root  crop  will  depend  a  great  deal  on 
how  it  is  prepared  for  the  table.  The  delicate  flavor  of 
the  sweet  potato  is  frequently  lost  through  poor  cooking. 
Steaming  preserves  the  flavor  better  than  boiling,  and 
baking  still  more  than  steaming.  The  sweet  potato, 
when  cooked  hurriedly,  is  tasteless.  A  short-time  bak- 
ing, for  instance,  may  satisfy  a  hungry  man  but  when 
flavor  is  desired,  longer  cooking  or  baking  should  be 
resorted  to.  The  following  are  various  recipes  taken 
from  Parloa  {77),  Carver  (9)  and  Fitz  (23)  and 
slightly  modified  by  Mrs.  A.  H.  Leidigh  of  College  Sta- 
tion, Texas. 

1.  Baked  Potatoes.  Wash  the  potatoes  with  a  brush 
in  running  water  until  thoroughly  clean.  They  are  then 
baked  like  white  potatoes  without  breaking  the  skin. 
When  done,  the  potato  is  cut  in  half,  buttered  and 
served  hot.  As  a  rule,  however,  baking  seems  to  be  bet- 
ter adapted  to  the  larger  round  and  irregular  sweet 
potatoes.  Small  potatoes  will  bake  in  about  half  an 
hour  where  very  large  ones  will  require  an  hour  or  more. 
If  potatoes  are  liked  moist  and  sweet,  they  should  be 
baked  one  to  two  hours,  the  exact  length  of  time  de- 
pending on  their  size. 

2.  Baked  in  Ashes.    With  this  method  the  sweetness 


Uses  of  the  Sweet  Potato  83 

and  taste  of  the  sweet  potato  is  brought  out  in  an  un- 
usual manner.  The  potatoes  are  merely  covered  with 
warm  ashes  to  a  depth  of  four  inches,  upon  which  live 
coals  and  embers  are  maintained.  Baking  is  done 
slowly  for  at  least  two  hours.  The  ashes  are  then  re- 
moved with  a  soft  brush  and  the  potatoes  are  served 
with  hot  butter. 

3.  Boiled  or  Steamed  Sweet  Potatoes.  Sweet  pota- 
toes are  boiled  or  steamed  in  the  same  way  as  Irish 
potatoes  and  without  breaking  the  skins.  When  boiling 
is  practical,  the  water  is  poured  off  as  soon  as  done  and 
the  potatoes  are  left  in  the  pot,  covered  with  a  plate,  and 
placed  on  the  back  of  the  range  until  served.  In  this 
way,  however,  the  cooked  sweet  potato  will  be  soggy. 
A  better  way  is  to  cover  the  cooked  roots  with  a  cloth 
for  a  few  minutes  before  serving. 

4.  Browned.  Medium-sized  sweet  potatoes  are 
boiled  for  forty  minutes.  They  are  then  peeled  and  cut 
lengthwise  into  halves.  These  are  placed  in  a  baking 
pan  and  basted  in  savory  drippings  and  seasoned  with 
salt.  They  are  cooked  in  a  hot  oven  for  twenty  minutes. 

5.  Fried.  The  potatoes  are  cut  lengthwise  into  slices 
and  fried  in  deep  grease  in  the  same  way  as  are  Irish 
potatoes,  care  being  taken  not  to  have  them  fried  too 
hard  and  dry. 

6.  Candied  Sweet  Potatoes.  This  mode  of  preparing 
sweet  potatoes  is  very  popular  in  the  South.  Candied 
potatoes  are  very  palatable  when  well  prepared.  They 
are  boiled  first  and  cut  into  long  slices,  which  are  placed 
in  an  earthen  dish.  On  each  slice  is  put  a  lump  of  butter 
and  a  sprinkling  of  sugar.  Some  prefer  to  add  a  little 
water.  It  is  placed  in  the  oven  and  baked  until  the  sugar 
and  butter  have  candied  and  the  potatoes  become 
browned. 


84 


The  Sweet  Potato 


7.  Chips.  Potatoes  are  cut  into  thin  slices,  and 
steamed  until  nearly  done.  The  surplus  water  is 
drained  off  and  the  steamed  potatoes  are  dried  between 
napkins.  Fry  in  deep  grease  to  a  light  brown.  A  little 
salt  is  added.    This  makes  a  delicious  breakfast  dish. 

8.  Sweet  Potato  Pie  No.  i. 

r  pt.  cooked  sweet  potato  pulp  4  eggs,  well  beaten 

I  pt.  milk  1 1  cups  sugar 

^  pt.  cream  Ginger,  cinnamon  and  cloves 

to  taste 

Boil  potatoes  in  skins.  When  tender  peel,  mash,  and 
beat  until  light.  Add  other  ingredients  and  bake  with 
bottom  crust  only.  This  makes  five  or  six  pies.  Spices 
may  be  omitted  or  less  sugar  may  be  used  if  desired. 

9.  Pie  No.  2.  The  following  recipe  given  by  Fitz  is 
from  Arkansas  and  is  as  follows : 


I  qt.  boiled  strained  potato  pulp       |  nutmeg  grated 
3  eggs  i  teaspoon  cinnamon 

3  tablespoons  sugar  |  teaspoon  cloves 

I  tablespoon  butter 
Lemon  peel  or  essence  of  lemon 

Add  cream  or  milk  to  make  a  mixture  the  consistency  of 
butter.  This  is  poured  into  a  baking  plate  and  baked 
with  two  crusts. 

10.  Sliced  Potato  Pie. 


Sweet  potatoes  i  cup  cream 

Butter  size  of  hen's  egg  {\  cup)  Flour  (a  little) 

I  cup  sugar  Hot  water 

\  cup  molasses  All-spice,    ginger,    cloves    and 

nutmeg 

Line  deep  baking  dish  with  rich  pastry.  Boil  sweet 
potatoes  until  two-thirds  done,  remove  skins,  and  slice 
very  thin  lengthwise.     Fill  the  dish  to   a  depth   of   2 


Uses  of  the  Sweet  Potato  85 

inches.  Add  other  ingredients,  and  enough  hot  water  to 
cover.  Put  on  upper  crust  and  crumple  edge.  Bake 
in  moderate  oven  until  done  and  serve  hot,  with  or 
without  sauce. 

11.  Glazed  No.  i.  Medium-sized  sweet  potatoes  are 
boiled  and  cut  into  halves.  These  are  laid  evenly  in  a 
braising  pan,  basted  with  syrup  and  butter  warmed  to- 
gether, and  sprinkled  lightly  with  brown  sugar.  The 
whole  is  put  in  a  hot  oven  until  brown  and  served  with 
syrup. 

12.  Glazed  No.  2.  Potatoes  are  cut  in  slices  one-half 
inch  thick,  washed,  and  placed  in  a  deep  sauce-pan. 
They  are  spread  with  butter  and  seasoned  with  a  little 
grated  nutmeg  and  salt,  and  moistened  with  broth  or 
water.  The  pan  is  then  covered  and  allowed  to  simmer 
over  a  slow  fire  for  three-fourths  of  an  hour.  Turn  the 
slices  so  that  they  are  glazed  on  both  sides.  They  are 
served  with  drawn  butter  or  other  sauce. 

13.  Sweet  Potato  Cobbler.  The  potatoes  are  prepared 
in  the  same  way  as  for  No.  8.  The  dish  is  then  filled 
in  the  same  way  as  for  layer  cake,  rolling  out  a  layer 
of  dough  quite  thin  and  then  spreading  the  mixture  in 
layers  about  one-fourth  of  an  inch  thick.  This  is  done 
until  the  dish  is  full.  To  each  layer  is  added  just 
enough  water  to  cook  the  layer  of  crust.  The  whole  is 
baked  until  thoroughly  done  and  served  hot  with  drawn 
butter  or  hard  sauce. 

14.  Sweet  Potato  with  Roast  Beef  No.  i.  The  beef 
is  roasted  and  a  brown  gravy  made.  Medium-sized 
baked  potatoes  are  then  peeled  and  served  on  the  dish 
with  the  roast. 

15.  SiaSeet  Potatoes  with  Roast  Beef  No.  2.  The  de- 
sired number  of  sweet  potatoes  are  parboiled  until 
nearly  done.    They  are  then  moved  from  the  fire  and 


S6  The  Sweet  Potato 

peeled  and  laid  in  a  baking  dish  with  the  nearly  done 
roast,  and  cooked  until  done  and  then  served  with  the 
beef. 

i6.  Sweet  Potato  with  Roast  Lamb.  A  desirable 
piece  of  fresh  lamb  is  selected  and  baked  until  nearly 
done.  Some  of  the  grease  is  poured  off.  The  potatoes 
are  prepared  in  the  same  way  as  for  No.  15.  They  are 
laid  in  the  gravy  and  slightly  browned  with  the  meat 
until  done. 

17.  Broiled.  Sweet  potatoes  are  steamed,  pared,  and 
cut  in  slices  three-eighths  of  an  inch  thick.  The  slices 
are  laid  in  a  double  broiler,  salted,  covered  with  melted 
butter,  and  broiled  over  a  slow  fire.  Serve  hot  in  folded 
napkins. 

18.  Stuffed  No.  I.  The  potatoes  are  baked,  one  end 
is  cut  off,  and  the  inside  removed.  This  pulp  is 
then  seasoned  with  butter,  pepper  and  salt,  and  beaten 
until  light  and  filled  into  the  skins,  which  are  closed  with 
the  cut-off  piece,  and  put  into  the  oven  to  heat  through. 
Serve  in  napkins.    These  are  suitable  for  luncheon. 

19.  Stuffed  No.  2.  This  is  prepared  the  same  way  as 
No.  18.  Add  to  every  pint  of  potato  Y^  cup  of 
minced  meat  and  mix  thoroughly.  Fill  the  skins,  heat, 
and  serve. 

20.  Southern  Dish.  Cut  baked  sweet  potatoes  into 
slices  and  put  into  an  earthen  dish.  To  each  layer  are 
added  sugar  and  butter  and  the  whole  is  baked  until 
slightly  brown. 

21.  Croquettes.  To  two  cupfuls  of  mashed,  boiled, 
steamed  or  baked  sweet  potatoes,  the  beaten  yolks  of 
two  eggs  are  added  and  the  whole  is  seasoned  to  taste. 
This  is  stirred  over  the  fire  until  the  mass  separates 
from  the  pan.  When  cold  it  is  formed  into  small  cro- 
quettes, rolled  in  tgg  and  bread  crumbs,  and  fried  in 


Uses  of  the  Sweet  Potato  87 

hot  grease  until  of  an  amber  color.    They  are  served 
in  napkins. 

22.  Sweet  Potato  Balls.  These  are  prepared  in  the 
same  way  as  croquettes;  they  are  made  into  balls  with 
minced  meat  in  the  center. 

23.  Puree.  Boiled,  steamed,  or  baked  sweet  potatoes 
are  mashed  and  seasoned;  enough  hot  milk  is  then 
added  to  moisten.  They  are  then  served  like  mashed, 
white  potatoes.  They  may  also  be  put  in  a  pudding 
dish  and  top-dressed  with  ^gg.  After  they  have 
browned  in  an  oven,  they  are  then  served  with  sauce. 

24.  Browned.  Cold  boiled,  or  steamed  sweet  pota- 
toes are  cut  into  slices  one-fourth  of  an  inch  thick. 
Add  butter,  sugar,  pepper  and  salt,  and  put  in  a  hot 
oven  to  brown. 

25.  Scalloped  Sweet  Potatoes.  The  potatoes  are 
washed,  peeled,  and  sliced  very  thin.  They  are  then 
put  in  layers  in  a  baking  dish  and  each  layer  seasoned 
with  salt,  butter,  one-half  teacup  of  sugar,  a  dash  of 
spice,  nutmeg,  and  ginger  and  covered  with  equal  parts 
of  milk  and  cream.  This  is  baked  in  a  moderate  oven 
until  tender  and  then  served  hot. 

26.  Browned.  Small-sized  potatoes  are  washed  and 
pared.  They  are  then  steamed  or  boiled  until  they  can 
be  readily  pricked  with  a  fork.  The  surplus  water  is 
then  dried  off  and  the  potatoes  rolled  in  a  dish  with 
melted  butter  and  placed  in  a  quick  oven  until  slightly 
browned.    They  are  then  served  hot. 

2^.  Hashed  Potatoes.  Cold  potatoes  steamed,  boiled, 
roasted,  or  baked,  are  cut  into  small  pieces  and  placed  in 
a  well-buttered  pan.  Stir  in  minced  scraps  of  meat  of 
any  kind.  This  is  allowed  to  brown  and  is  then  served 
hot.    Chicken  is  the  most  excellent  meat  to  put  in  it. 


88  The  Sweet  Potato 

28.  Baked  with  Apples. 

4  medium-sized  potatoes  §  cup  butter 

4  apples  1 1  cups  hot  water 

1  §  cups  sugar 

Wash  and  peel  the  potatoes  and  apples  and  cut  in 
^-inch  slices.  Put  into  a  baking  dish  in  alternate 
layers,  sprinkling  each  with  butter  and  sugar.  Add 
water  and  bake  slowly  for  an  hour  and  serve  steaming 
hot. 

29.  Sweet  Potato  Pudding. 

2  cups  mashed  boiled  sweet  pota-       i  cup  cream 

toes  I  teaspoon  cimiamon 

I  cup  sugar  i  grated  nutmeg 

I  cup  butter  i  teaspoon  lemon  extract 

4  eggs 
Pinch  of  soda  dissolved  in  I  tea- 
spoon water 

To  the  hot  potato  pulp,  add  sugar,  creamed  butter, 
eggs  beaten  light,  and  other  ingredients.  Bake  in  a  deep 
plate  lined  with  puff  paste,  using  a  moderate  oven. 
When  done,  the  top  is  covered  with  slices  of  fruit  mar- 
malade and  sprinkled  thickly  with  granulated  sugar. 

Sweet  Potato  Syrup.  The  feasibility  of  making  syrup 
from  sweet  potatoes  was  demonstrated  by  the  Bureau 
of  Chemistry  (6)  of  the  United  States  Department  of 
Agriculture.  The  syrup  is  claimed  to  be  palatable  and 
wholesome.  The  method  was  developed  by  a  specialist 
of  the  Bureau  of  Chemistry  and  is  only  recommended 
on  a  small  scale,  as  it  could  not  compete  with  syrups 
made  on  a  commercial  basis  from  grains.  The  sweet 
potato  syrup  has  a  consistency,  taste,  and  color  similar 
to  cane  and  sorghum  syrups. 

The  Method  in  Brief.  The  sweet  potatoes  should  be 
washed,  any  decayed  portions  or  other  blemishes  re- 


Uses  of  the  Sweet  Potato  89 

moved,  and  weighed.  They  are  then  placed  in  a  kettle 
with  plenty  of  water  and  boiled  until  thoroughly  soft. 
One  and  one-half  to  two  hours  are  required.  The  pota- 
toes are  then  mashed  in  the  kettle  in  the  water  in  which 
they  were  boiled.  More  water  should  be  added,  if  neces- 
sary, to  form  a  thick,  smooth,  mushy  liquid.  The  tem- 
perature of  the  mixture  is  then  brought  to  140  degrees 
F.,  and  a  quantity  of  ground  malt  added,  equal  to  3^ 
per  cent  of  the  weight  of  the  original  sweet  potatoes. 
The  mixture  is  thoroughly  stirred  and  allowed  to  stand 
for  a  few  minutes  at  a  temperature  of  140  degrees  F., 
and  with  constant  stirring  raised  to  150  degrees  F.  The 
source  of  heat  is  then  removed,  and  the  mass  allowed  to 
stand  with  occasional  stirring  for  an  hour.  The  mix- 
ture known  technically  as  the  "mash"  is  now  pressed 
in  cloth  to  separate  the  liquid  and  solid  portions.  The 
material  is  placed  in  a  closed  cloth  bag,  and  the  bag  sub- 
jected to  gentle  pressure  while  being  kneaded.  The 
juice  flows  out  readily,  leaving  the  pulp  behind.  The 
juice  is  now  boiled  down  to  syrup  in  an  ordinary  kettle. 

Any  of  the  common  varieties  of  sweet  potatoes  can 
be  used.  Freshly  harvested  stock  will  yield  a  syrup 
somewhat  less  sweet  than  sweet  potatoes  which  have 
been  harvested  for  some  time. 

The  sweet  potatoes  should  be  cooked  with  plenty  of 
water.  It  is  necessary  to  obtain  a  fluid,  mushy  mass, 
which  can  be  mixed  readily  with  the  malt. 

Great  care  must  be  taken  that  the  temperature  of  the 
mass  be  uniform  throughout  during  the  action  of  the 
malt. 

Preparation  of  Malt  Ordinary  brewer's  or  distiller's 
malt  of  good  quality  gives  excellent  results,  or  the  malt 
can  be  made  by  sprouting  barley  under  proper  condi- 
tions.   In  the  preparation  of  malt  from  barley  the  fol- 


90  The  Sweet  Potato 

lowing  method  will  give  satisfactory  results :  The  grain 
should  be  soaked  in  water  for  twelve  hours.  The  water 
is  then  drained  off  and  the  grain  allowed  to  stand  for 
twelve  hours,  and  the  operation  of  soaking  and  standing 
repeated  during  the  next  twenty-four  hours.  At  the 
conclusion  of  the  steeping,  the  interior  of  the  grain  is 
then  spread  upon  a  tray  in  a  layer  not  over  six  or  eight 
inches  deep.  The  temperature  at  which  the  sprouting 
grain  is  kept  is  of  great  importance  in  the  successful 
manufacture  of  malt.  It  should  be  kept  as  near  60  de- 
grees F.  as  possible.  After  the  grain  has  grown  for 
six  or  eight  days  the  sprout  forces  its  way  out  of  the  end 
of  the  grain  opposite  to  the  rootlet,  and  the  malt  may 
be  used  with  excellent  results  at  this  time.  Sprouting, 
however,  may  be  allowed  to  continue  slowly  for  an- 
other six  or  eight  days,  or  even  longer,  until  the  sprout 
has  attained  a  length  three  to  four  times  that  of  the 
grain.  The  grain  must  be  kept  moist,  so  that  the  root- 
lets do  not  wither  during  the  sprouting  period  and 
should  be  turned  over  and  thoroughly  mixed  at  least 
once  a  day  and  kept  covered  with  a  wet  cloth  and  in 
the  dark.  The  product  is  known  as  "green  malt."  It 
should  have  a  fresh  odor  and  be  free  from  any  sour 
smell,  and  should  be  free  from  mold.  Immediately  be-" 
fore  use,  the  green  malt  should  be  ground  finely  in  an 
ordinary  meat  chopper  or  other  suitable  machine.  When 
so  ground  it  forms  a  pasty  mass  and  may  be  added 
directly  to  the  boiled  mashed  sweet  potatoes  and  the 
mixture  thoroughly  stirred. 

Separating  the  Liquor.  On  a  small  scale  this  is  most 
readily  accomplished  as  described.  On  a  large  scale  an 
ordinary  cider  press,  using  racks  and  cloths,  can  be  suc- 
cessfully employed.  The  liquor  obtained  is  slightly 
sweet  and  rather  turbid.     Plenty  of  water  should  be 


Uses  of  the  Sweet  Potato 


91 


used  in  order  to  produce  a  mash  from  which  the  liquor 
will  flow  freely  and  in  which  a  large  proportion  of  the 
sugar  may  be  easily  removed  by  a  single  pressing.  The 
total  quantity  of  water  used  should  be  two  or  three  times 
the  weight  of  the  potatoes.  The  sweet-potato  syrup  can 
be  boiled  down  to  as  thick  a  consistency  as  desired.  The 
pulp  which  remains  can  be  dried  and  used  for  feed,  or 
it  can  be  fed  to  cattle  while  fresh. 

Not  only  is  the  sweet  potato  a  valuable  food  for 
humans,  but  it  can  also  serve  a  similar  purpose  for 
stock.  Varieties,  such  as  Enormous  and  Nigger  Choker, 
are  high  yielders  and  could  be  grown  as  stock  feed. 

Sweet  Potato  Vines  for  Forage 

If  it  were  not  for  the  great  expense  in  harvesting 
sweet  potato  vines  they  would  make  an  excellent  forage 
or  hay,  which  is  greatly  relished  by  stock.  Table  i8  by 
Keitt  (58)  gives  the  composition  of  the  vines  of 
four  varieties  of  sweet  potatoes. 


Table  18 
Composition  of  Sweet  Potato  Vines 


Name  of  Variety 

Protein 

Fat 

Fiber 

Ash 

Nitrogen 

Free 
Extract 

Total 

Per 
Cent. 
12.30 
14.28 
11.28 
12.07 

Per 

Cent. 

Vi 

4-34 
5.05 

Per 
Cent. 
17.10 
17.98 
18.70 
19. II 

Per 
Cent. 
9.78 
9.06 
8.04 
8.03 

Per 

Cent. 
55  67 
53-80 
57-64 
55-74 

Per 

Cent. 

Polo 

Southern  Queen 

Nancy  Hall 

100.00 

Average 

12.48 

.4.86 

18.22 

8.37 

SS.71 

100.00 

92 


The  Sweet  Potato 


On  account  of  the  expense  of  gathering  the  vines,  they 
are  more  profitably  plowed  under,  and  serve  as  a  valu- 
able source  of  humus  in  the  soil. 

Sweet  Potato  Silage 

It  has  been  previously  stated  that  the  sweet  potato 
could  be  used  as  a  stock  food.  The  work  of  Scott  (86) 
has  shown  that  it  can  be  more  profitably  grown  as 
stock  feed.  Sweet  potatoes  were  first  put  in  the  silo  of 
the  Florida  Experiment  Station  in  191 7.  Analysis  of 
corn  and  sweet  potato  silage  is  as  follows : 


Silage 

Moisture 

Crude 
Protein 

Nitrogen 

Free 
Extract 

Fiber 

Fat 

Ash 

Sweet  potato 

Com  . . 

Per 

Cent. 
54-87 
73-7 

Per 
Cent. 
1.82 
2.1 

Per 
Cent. 
39-41 
15-4 

Per 
Cent. 
1.48 

9.3 

Per 

Cent. 
0.66 
0.8 

Per 
Cent. 
1.85 
1-7 

From  the  above  figures  it  is  evident  that  there  is  but 
little  difference  in  the  feeding  value  of  the  two.  But, 
100  pounds  of  sweet  potato  silage  will  replace  150  to 
200  pounds  of  corn  silage  in  the  ration.  This  is  due  to 
the  fact  that  sweet  potato  silage  contains  less  water  and 
two  and  a  half  times  more  nitrogen-free  extract  than 
the  corn  silage. 

To  determine  the  milk  production  from  sweet  potato 
and  sorghum  silage,  Scott  made  the  following  tests 
(May  9  to  June  20),  lasting  forty-three  days.  The 
test  was  made  in  two  periods  of  twenty  days  each  with 
three  days  between  periods  for  the  purpose  of  changing 
feed.    Ten  cows  were  used  and  divided  into  two  lots  of 


Uses  of  the  Sweet  Potato 


93 


five  each.  Each  cow  in  Lots  I  and  II  was  given  the  fol- 
lowing daily  ration  as  shown  in  Table  19. 


Table  19 

Lot  I 

Pounds 

Lot  II 

Pounds 

Wheat  bran 

10.6 

Wheat  bran 

1:1 

15-2 

Cottonseed  meal 

Sweet  potato  silage 

Cottonseed  meal 

Sorghum  silage 

During  the  second  period  the  feeds  were  reversed,  that 
is,  the  cows  in  Lot  I  were  given  the  feed  of  Lot  II,  and 
Lot  II  the  feed  of  Lot  L  Cows  fed  on  sweet  potato 
silage  produced  307.1  gallons  of  milk.  Cows  fed  on 
sorghum  silage  produced  280.9  gallons  of  milk;  a  dif- 
ference of  26.2  gallons  in  favor  of  the  sweet  potato 
silage.  The  feed  used  in  the  above  experiment  was 
charged  as  follows :  wheat  bran  $40.00,  cottonseed  meal 
$50.00,  corn  silage  $4.00,  and  sweet  potato  silage  $13.33 
a  ton.  At  this  rate  the  feed  cost  of  a  gallon  of  milk 
produced  by  the  corn  silage  ration  was  11.8  cents,  by 
sweet  potato  silage  14.2  cents.  The  difference,  however, 
in  cost  of  production,  was  due  to  the  high  price  charged 
to  the  sweet  potato  silage.  Sweet  potato  silage  saves 
considerable  storage  space  and  dispenses  with  all  losses 
from  rots. 

Sweet  Potato  Starch 

The  sweet  potato  as  a  starch  crop  has  re'ceived  but 
little  attention.  During  the  Civil  War,  a  small  amount 
of  impure  starch  was  made  in  the  Southern  States.  Mc- 
Donnell (66)  was  practically  the  first  to  consider  the 
manufacture  of  sweet  potato  starch  on  a  commercial 


94  The  Sweet  Potato 

basis.  Starch  is  greatly  in  demand  by  the  cotton  manu- 
facturers, and  it  is  used  in  ''sizing"  yarn  and  in  "filHng 
cloth."  The  product  generally  used  is  either  Irish  po- 
tato or  com  starch.  All  the  high-yielding  varieties  of 
sweet  potatoes  which  are  poor  for  table  purpose  could 
be  grown  as  starch  producers. 

Process  of  Manufacture.  The  machinery  used  for  the 
manufacture  of  starch  from  Irish  potatoes  may  also  be 
adapted  for  the  same  purpose  for  sweet  potatoes.  On  a 
large  scale,  the  potatoes  are  first  run  through  a  washer 
and  all  dirt  and  sand  removed  (Fig.  5,  a).  From  the 
washer  they  are  carried  and  dumped  into  a  hopper,  or 
pulping  machine  (Fig.  5,  b).  The  thin  pulp  coming  from 
the  pulping  machine  is  made  to  fall  on  an  inclined  sieve 
(Fig.  5,  i.)  of  fine  wire  gauze,  having  eighty  meshes  to 
the  inch.  Above  the  sieve,  water  is  thrown  on  the  pulp, 
which  separates  the  small  starch  granules  and  washes 
them  through  the  sieve  (Fig.  6,  i.).  The  white  starchy 
liquid  falls  from  the  sieve  into  a  tank,  and  from  there 
is  pumped  into  settling  tanks.  These  are  about  fifty 
feet  in  diameter  and  eighty  feet  deep.  After  a  few 
hours'  standing,  the  starch  settles  down,  and  the  dirty 
colored  water  is  siphoned  off.  The  starch  is  then 
transferred  to  washing  tanks,  where  it  is  washed  several 
times  in  fresh  water,  which  is  siphoned  off  after  the 
starch  has  settled.  The  purified  material  is  then  trans- 
ferred in  trays  to  dry  kilns  (Fig.  5,  j.)  and  left  there 
until  the  moisture  has  been  reduced  to  ten  or  twelve  per 
cent.  The  dry  kiln  is  heated  by  steam  coils,  which  do 
away  with  the  danger  of  fire.  The  temperature  during 
drying  should  never  be  higher  than  150  degrees  F. 
When  the  dried  starch  has  been  removed  from  the  kiln, 
it  is  piled  up  in  warehouses  in  order  that  the  moisture 
may  be  evenly  distributed  through  the  mass.    It  is  then 


Fig.  s.    Swket  Potato  Starch  Factory. 
A.  Tank  for  washing  potatoes.     B.   PulpiiiK  niarhinr.     r.  Starch  separator. 
D.  Receptacle   for  starch  milk.     E.  Steam    pipe     /''.  Suirch  washmg    tank"^ 
G.  Motor.     //.  Pulper.     /.Sieve.     7.  Drying  house.     A'.  Sweet  potato  starch 
grains.     L.  Corn  starch  grains.     M .  Irish  potato  starch  grains, 
after    McDonnell  I.      N.   Diagram   illustratinj; 
(after  Lani^'worlhyi. 


(.1    to    M, 
composition   of   sweet   potato 


Uses  of  the  Sweet  Potato 


95 


barreled  and  ready  for  market.  Table  20  by  McDonnell 
(66)  shows  the  amount  of  starch  obtained  per  bushel 
from  Southern  Queen  and  Red  Nancemond. 

Table  20 
Amount  of  Starch  from  Different  Varieties 


Variety 

Quantity 

Operated 

upon 

Total 
Starch 

in 
Potatoes 

Total 
Starch 

Re- 
covered, 

Com- 
mercial 

Starch 
Remain- 
ing in 
Pulp 

Starch 
Lost  in 
Wash 
Water, 
etc. 

Total 
Weight 
Dried 
Pulp 

Southern  Queen.. 
Southern  Queen. . 
Red  Nancemond. . 

Bushels 
26 
17 
13 

Pounds 
321.6 
224.7 
127.3 

Pounds 

184.0 

154.0 

80.0 

Pounds 
III. 8 
78.3 
43.3 

Pounds 

415 
6.6 

8.5 

Pounds 

182.0 

121. 8 

84.0 

Providence 

Southern  Queen . . 
Triumph 

8.2 
12.5 
15 

104. 1 
161. 0 
202.8 

76.0 
100. 0 
137.0 

17. 1 
31.7 
42.3 

22.6 
43.3 
47.8 

32.8 
570 
750 

Starch  from  the  sweet  potato,  like  that  of  the  Irish 
potato,  may  be  bleached  with  sulphur  dioxide,  sulphur- 
ous acid,  or  bleaching  powder  and  sodium  hypo-sulphite. 
It  is  also  often  treated  with  dilute  alkalies,  sodium  hy- 
drate, or  lime  water  to  dissolve  the  gums  and  all  other 
impurities. 

Sweet  potato  starch  grains  slightly  resemble  the 
grains  of  corn  starch  (Fig.  5,  1.).  They  are,  however, 
more  variable  in  size  and  not  so  angular.  The  hilum  is 
well  developed,  and  is  cross-  or  star-shaped  (see  com- 
parisons of  Figs  5,  k.). 

Uses  for  Sweet  Potato  Starch 

For  the  laundry,  sweet  potato  starch  is  ideal.  It  makes 
a  paste  quickly.    Three-quarters  of  a  pound  goes  as  far 


96 


The  Sweet  Potato 


as  a  pound  of  the  laundry  starch  from  corn  or  Irish  po- 
tatoes ^Fig.  5,  m).  It  also  penetrates  the  goods  much 
better.  It  does  not  adhere  to  the  surface  of  starched 
collars  or  cuffs.  The  starched  articles  do  not  adhere  to 
the  rollers  when  surface  starch  is  not  wiped  off.  The 
finished  laundry  does  not  crack  when  bent.  Sweet  po- 
tato starch  is  also  admirably  adapted  for  sizing  yarns, 
filling  cloth,  and  thickening  colors,  in  cotton  mills  and 
print  shops. 

Table  21 


Shoiving   Calculated   Yield  per  Acre,   Per  Cent.   Glucose, 

Sucrose,  Starch,  Total  Fermentable  Carbohydrates  and 

Yield  Calculated  from  the  Carbohydrates  of 

Gallons  of  Alcohol  per  Acre 


Variety 

Rate  of 

Yield 

per  Acre 

in 
Bushels 

Per 

Cent. 
Glucose 

Per 

Cent. 

Sucrose 

Per 

Cent. 
Starch 

Per 
Cent. 
Fer- 
mentable 
Carbo- 
hydrates 

Theo- 
retical 
Yield  in 
Gallons 

of 
Alcohol 
per  Acre 

Nancv  Hall        

270.0 
281.0 
416.0 
141. 0 
191. 0 
450.0 
158-0 
281.0 
214.0 
180.0 

270.0 
1740 
141. 0 
326.0 

1.53 
1.75 
I-5I 
0.55 
0.31 
1.22 
1.78 
2.00 
1.36 
1.44 

1.69 
0.49 
1.83 
0.52 

2.35 
2.02 
2.18 
3-36 

i:tl 

Ul 

3.66 
2.77 
323 
336 

17.82 
14.85 
19.07 
20.05 
17.30 
16.46 
14-43 
16.71 
13-50 
19.40 

20.63 
23.89 
19.22 
18.72 

21.70 
18.62 
22.76 
23.96 
21.70 
20.57 
18.64 
21.09 
18.64 
23.02 

25-98 
27-15 
24.28 
22.60 

292.1 

Polo 

260.0 

Southern  Queen . .  .\  . 

White  Spanish 

General  Grant 

Tirayilian                    .... 

473-5 
169.5 
207.5 
262.2 

Arkansas  Beauty 

Tennessee  Notchleaf . 
Yellow  Nancemond, . 

Purple  Yam 

Pumpkin  Early  Yel- 
low Yam 

152.7 

198!  I 
207.4 

343-6 

Shanghor  Yam 

Vineland  Bunch  Yam. 
Fulleton  Yellow  Yam. 

181. 1 
167.6 
369.3 

Uses  of  the  Sweet  Potato  97 

The  by-product  of  sweet  potato  starch  is  the  pulp. 
This  can  be  used  as  a  feed  for  stock,  or  for  making 
alcohol.  One  bushel  of  pulp  would  yield  about  one-half 
gallon  of  95  per  cent  alcohol.  This  should  be  looked  to 
in  the  future  as  an  important  source  of  fuel  in  the 
various  industries.  Table  21  by  Keitt  (58)  is  very 
suggestive  of  the  amount  of  starch  and  alcohol  to  be 
obtained  from  the  total  of  varieties. 


Location  of  Starch  Factories 

The  essential  requirements  in  the  location  of  starch 
factories  are  as  follows  : 

1.  Factory  should  be  located  near  source  of  sup- 
plies. Sweet  potatoes  are  very  bulky  and  do  not 
stand  long  shipment. 

2.  A  good  water  supply  free  from  suspended  or- 
ganic matter,  algae,  salts,  and  iron. 

3.  Cheap  transportation  facilities,  both  rail  and 
water. 

4.  Factory  should  be  located  on  or  near  a  stream 
to  dispose  of  the  waste  water. 

5.  Dependable  labor  and  markets. 

Owing  to  the  growth  of  the  textile  enterprise,  sweet 
potato  starch  should  find  there  its  best  home  markets. 


PART  II 
DISEASES 


CHAPTER  VII 

MORPHOLOGY  OF  THE  HEALTHY  HOST 

To  gain  a  clear  understanding  of  the  diseases  of  the 
sweet  potato,  and  especially  of  the  effect  of  parasite  on 
host,  it  is  necessary  to  study  the  structure  of  the  healthy 
plant.  The  author  has  devoted  considerable  study  to 
this  phase,  and  his  observations  practically  agree  with 
the  studies  made  by  Groth  (26). 

The  root.  By  root  is  here  meant  the  edible  portion  of 
the  sweet  potato.  The  latter  is  not  a  tuber,  as  is  often 
stated  in  literature,  but  is  a  thickened  root,  fascicular  to 
spherical,  veiny  or  smooth,  3  to  6  lobed  in  cross-section. 
The  root  lenticels  are  either  conspicuous  or  very  small ; 
the  dormant  shoots  are  situated  near  the  lenticels.  The 
shoots  appear  first  at  the  tip  end,  but  later  come  out  ir-- 
regularly  from  every  direction.  The  color  of  the  edible 
roots  is  white,  yellowish  to  pinkish-white,  or  bronze, 
light  to  dark  purple,  flesh,  cream-colored,  pinkish-white, 
pinkish-orange.  The  cambium  and  wood  elements  are 
white,  dirty  white,  yellow,  or  orange,  distinct  or  indis- 
tinct.   The  flesh  is  soft  or  hard. 

When  a  thin  cross  section  of  a  young  rootlet  is  placed 
under  a  microscope,  the  xylem  is  found  to  be  very 
prominent,  usually  arranged  in  five  patches,  and  sep- 
arated as  it  were  by  medullary  rays. 

In  a  cross  section  of  an  edible  root,  the  xylem  ele- 
ment appears  in  groups  or  isolated,  each  surrounded  by 
actively  growing  tissue  in  the  midst  of   fundamental 


102  The  Sweet  Potato 

tissue.  The  cells  in  both  growing  and  fundamental  tis- 
sues are  gorged  with  compound  starch  grains.  The 
cambium  element  is  situated  outwardly  towards  the  epi- 
dermis, with  the  ring  of  xylem  either  radiating  towards 
the  center  or  not.  Frequently  five  or  more  groups  of 
xylem  element  run  in  strands  outside  of  the  cambium 
layer,  forming  longitudinal  ridges  known  as  veins. 

The  stem.  The  stem  or  vine  growth  varies  from 
twenty  feet  or  more  in  some  varieties  to  about  two  feet 
in  the  bunch  varieties.  Its  diameter  varies  from  ^  to 
more  than  Y^  inch  at  its  largest  parts.  In  some  varieties 
f asciation  is  a  common  occurrence ;  in  others  the  vines 
strongly  twine,  run,  or  grow  in  clumps.  The  color  varies 
from  light  green  throughout  to  dark  purple  all  over, 
with  gradations  of  purple  below  the  attachment  of  the 
petioles.  Lenticels  are  abundant;  hairs  are  present  in 
young  shoots  and  may  be  persistent.  New  roots  may 
develop  on  each  joint  on  the  two  opposite  sides  of  the 
stem.  With  a  long  favorable  season  these  roots  may  de- 
velop into  small  or  medium-sized  potatoes. 

A  microscopical  study  of  a  cross-section  of  the  tip  of 
a  stem  will  reveal  numerous  glands  on  the  epidermis. 
Hairs  are  also  present  and  their  abundance  depends  on 
the  variety.  Epidermal  cells  are  thin-walled.  The  one 
or  two  layers  of  hypodermis  are  always  well  marked. 
The  cortex  is  loose  with  intercellular  spaces  and  con- 
tains well-marked  milk  or  latex  canals,  each  of  which 
is  composed  of  four  to  six  secreting  cells.  The  en- 
dodermis  is  sharply  marked,  and  below  is  an  interrupted 
one-to-three-celled  layer  of  very  thin-walled  pericam- 
bium.  The  xylem  is  well  developed.  The  internal 
phloem  consists  of  small  isolated  patches  of  dividing 
cells  among  pith  cells  smaller  than  the  rest.  The  pith 
also  contains  latex  canals  and  large  cells  with  intercel- 


Fig.  6.    Morphology  of  Healthy  Host. 

a,  b,  and  c.  Surface  view  of  epidermis  showino;  arrangement  of  stomata. 
d.  Cross-section  through  sweet  potato  leaf.  e.  Cross-section  through  sweet 
potato  leaf  vein.  /.  Cross-section  through  leaf  petiole,  g.  Lenticel  or  pro- 
liferation of  the  epidermis  of  old  stem  of  Georgia,  h.  Diagram  of  cross- 
section  of  base  of  stem  of  Florida,  i.  Cross-section  of  old  stem  of  Southern 
Queen,     (a  to  i  after  Groth.) 


Morphology  of  the  Healthy  Host    103 

lular  spaces.  Few  or  no  crystals  are  evident  in  the 
young  tips. 

At  the  base  of  an  old  stem,  the  epidermis  contains  few 
gland  cells,  and  bears  few  or  no  hairs  but  has  numerous 
lenticels.  The  epidermal  cells  are  thin-walled  and  the 
hypodermis  is  more  prominent  and  has  no  or  few  crys- 
tal cells.  The  coUenchyma  sheath  is  composed  of  three 
to  five  outer  layers  of  cortex.  The  latex  or  milk  canals 
are  either  flattened  or  well  preserved.  The  secreting 
cells  are  either  well  preserved  or  they  have  disappeared. 
The  endodermis  is  well  marked.  The  pericambium  is 
composed  of  a  ring  of  strongly  thickened  fibers  in  some 
varieties  and  of  thin  fibers  in  others.  The  phloem  is 
unevenly  distributed  in  thickness  with  or  without  crys- 
tals and  occasionally  with  a  few  latex  canals.  The 
cambitfm  is  strongly  marked,  the  xylem  wide  or  narrow, 
sometimes  without  or  with  vessels  which,  when  present, 
are  filled  with  tyloses.  The  xylem  cells  show  spiral  and 
reticulated  thickenings  as  well  as  bordered  pits.  Xyleni 
cells  are  not  lignified  uniformly,  the  crystal  cells  occur- 
ring in  the  unlignified  cells.  The  protoxylem  is  divided 
from  the  cambium  of  the  internal  phloem  by  patches  of 
narrow  areas  similar  to  fundamental  tissue  but  with 
cells  smaller  than  the  cells  of  the  pith.  The  funda- 
mental tissue  is  of  large  thin- walled  cells  with  large  in- 
tercellular spaces  and  many  latex  canals.  The  pith  cells 
are  connected  by  pore  plates,  and  are  often  divided  into 
chambers,  the  latter  of  which  contain  crystals  (Fig.  6,  h 
and  i). 

Leaf.  Normally  developed  leaves  vary  in  different 
varieties,  from  2j4  to  6  inches  or  more  in  their  widest 
diameter.    The  veins  are  palm-like  in  arrangement. 

Microscopically  the  epidermis  of  the  leaf  consists  of 
irregularly  shaped,  sinuate,  thin-walled  cells,  convex 


104  The  Sweet  Potato 

towards  the  outer  surface,  and  modified  in  shape  when 
elongated  over  bundle  traces,  or  radiating  from  gland 
cells,  or  surrounding  base  of  hairs,  showing  peculiar 
wall  striations.  The  stomata  are  located  on  both  surfaces 
(Fig.  6,  a,  b  and  c)  being  more  abundant  on  the  lower 
side  of  the  leaf.  The  stomata  often  show  successive 
divisions  of  surrounding  cells  and  guard  cells,  and 
sometimes  double  guard  cell  formation.  The  gland 
hairs  are  scattered  over  both  surfaces  of  the  leaf.  The 
mesophyll  consists  of  two  to  three  layers  of  palisade 
parenchyma  with  stomatic  chambers  in  which  may  be 
very  thin-walled  cells  containing  calcium  oxolate  crys- 
tals (Fig.  6,  dand  e). 

Petiole.  Petiolar  nectrarles  consist  of  invaginations 
of  the  epidermis,  forming  cavities  thickly  lined  with 
glandular  hairs.  There  are  many  latex  canals  in  the 
pith  of  the  petiole  tissue.  Crystal  cells  are  formed  in 
the  fundamental  tissue  near  the  bundles  and  in  the 
phloem  (Fig.  6,  f). 


CHAPTER  VIII 

LOSSES   FROM   SWEET   POTATO   DISEASES 

The  object  in  growing  any  crop  is  to  produce  as 
much  feed  and  food  and  to  clear  as  much  reasonable 
net  profit  as  possible.  The  drawbacks  in  farming  are 
poor  soils,  unfavorable  climatic  conditions,  and  plant 
diseases.  In  the  United  States  we  have  sufficient  good 
soils,  and  reasonably  dependable  weather  conditions  in 
the  sweet  potato  regions  to  produce  a  profitable  crop. 
On  an  average,  and  especially  under  present  conditions, 
prices  are  good,  and  the  demand  for  sweet  potatoes  is 
equally  so.  The  only  drawback,  therefore,  is  the  numer- 
ous diseases  which  cut  down  the  yields  in  the  field  and 
affect  keeping  in  storage. 

These  losses  are  caused  by  several  diseases,  the  prin- 
cipal ones  being:  Black  Rot,  Stem  Wilt,  Ground  Rot, 
also  known  as  "pox"  or  "pit,"  White  Rust,  Septoria 
Leaf  Spot,  Soft  Rot,  Charcoal  Rot,  and  Dry  Rot. 

The  estimate  of  losses  in  the  United  States  in  19 17 
from  stem  rot  (Fusarium  hyperoxysporum  and  F. 
hatatatis)y  black  rot  (Ceratostomella  fimbriata),  and 
storage  rots  caused  by  various  organisms  are  shown  in 
Table  22  * 

*  From  Plant  Disease  Bulletin  2  :  1-17,  1918. 
105 


io6 


The  Sweet  Potato 


Table  22 
Field  and  Storage  Losses 


State 


Pro- 
diiction, 

1917, 
Bushels 

{poo 
Omitted) 


Reduction  in  Yields  Due  to  Disease 


Stem  Rot 


Per 
Cent. 


Bushels 

(000 
Omitted) 


Black  Rot 


Per 

Cent 


Bushels 

{000 
Omitted) 


Storage  Rots 


Per 

Cent. 


Bushels 

(poo 
Omitted) 


New  Jersey 

Pennsylvania 

Delaware 

Maryland 

Virginia 

West  Virginia 

North  Carolina 

South  Carolina 

Georgia 

Florida 

Ohio 

Indiana 

Illinois 

Iowa., 

Missouri 

Kansas 

Kentucky 

Tennessee 

Alabama 

Mississippi 

Louisiana 

Texas 

Oklahoma 

Arkansas 

New  Mexico 

Califomia 

United  States. . . 
Other  diseases, 

United  States. . . 
Total  loss  due  to 

disease,     United 

States 


2,880 

no 

560 

i,i8o 

4,160 

280 

8,550 

7,600 

11,625 

3,500 

95 
318 
776 
270 
896 

368 

1,140 

2,850 

16,020 

5,525 
4,898 
6,552 

1,350 

4,400 

236 

1,002 

87,141 


ID 
O 

5 

5 

3 

o 

2 

2 

2 

2.5 

2 

o 

2 

5 
I 

2.5 

o 

o 

2 
2 
O 
I 

2 
2 
O 
2 

1.47 


320 

O 

29 

62 

129 

O 

174 

155 

237 

90 

2 

O 

16 

14 

9 

9 

o 

o 

327 

113 

O 

66 
28 
90 
o 
20 

1890 


5 
2 
5 
8 
4 
2 
7 
7 
5 
I 

2 
2 
4 
5 
2 

2.5 
o 

15 
8 
8 
4 
5 

4 
3 
10 
6 

436 


152 
2 

29 

103 

173 

6 

644 

572 

612 

35 

2 

6 

32 

14 

19 

9 
o 

503 
1393 
480 
204 
345 

56 
136 
26 
64 

5617 


24.6 
1.94 

32.37 


720 
o 

99 

208 

734 

o 

3.664 

3,257 

4,982 

35 

o 

o 

41 
o 
o 

41 

380 

950 

6,865 

2,368 

2,099 
2,808 

578 

1,886 
o 
o 


31,715 
2,484 

41,706 


Losses  from  Sweet  Potato  Diseases    107 

The  foregoing  figures  are  very  conservative  and 
speak  for  themselves.  From  this  is  apparent  the  im- 
portance of  reducing  these  losses,  so  as  to  increase  the 
nation's  food,  and  at  the  same  time  insure  a  more 
profitable  production.  This  can  be  done  by  the  grower 
making  a  study  of  his  business  and  by  giving  careful  at- 
tention to  the  diseases  which  cause  these  losses.  The 
various  sweet  potato  troubles  ;will  be  presented  in  de- 
tailed form,  and  the  causal  organisms  arranged  some- 
what in  their  botanical  order  (mycological). 

Pox,  OR  Pit  (Soil  Rot) 
Caused  by  Cystospora  batata,  Elliot 

Economic  Importance.  Next  to  the  black  rot  (Cera- 
tostamella  fimbriata),  and  stem  rot  (Fusarium  botatatis 
and  F.  hyperoxysporium) ,  pox,  or  pit,  may  be  considered 
an  important  and  serious  disease  of  the  sweet  potato. 
Until  recently  the  trouble  was  misunderstood,  being 
frequently  mistaken  for  black  rot.  For  this  reason  the 
exact  distribution  of  this  disease  and  the  money  losses 
caused  by  it  are  not  definitely  known. 

Pox  is  undoubtedly  of  great  economic  importance, 
but  estimates  of  the  money  losses  from  the  trouble  can 
not  be  given  for  all  the  States  where  sweet  potatoes  are 
grown.  It  may  be  safely  stated  that  in  fields  where  pox 
has  become  thoroughly  established,  the  yields  may  be 
reduced  by  about  50  to  80  per  cent.  The  writer  has  had 
occasion  to  make  such  estimates  in  many  sweet  potato 
fields  in  Delaware,  New  Jersey,  Maryland  and  Virginia. 

Geographic  Distribution.  There  seems  no  doubt  that 
pox  has  a  wider  geographical  distribution  than  is  at 
present  known.    It  can  probably  be   found  wherevei; 


io8  The  Sweet  Potato 

sweet  potatoes  grow.  In  New  Jersey,  Halsted  recorded 
it  as  a  very  serious,  well-distributed  disease.  In  Dela- 
ware it  is  as  yet  localized  in  Kent  County,  but  appears 
to  be  gradually  spreading  southward.  In  Virginia  the 
pox,  although  widespread,  is  at  present  localized  in  small 
areas.  In  Maryland  the  disease  was  recorded  by  Town- 
send  (107)  and  was  found  by  the  writer  to  be  a  seri- 
ous trouble,  vying  in  importance  with  black  rot.  In 
South  Carolina  pox  was  reported  by  Barre  (2).  In 
Texas  it  had  been  previously  reported  by  Price  (79) 
and  from  the  writer's  own  observation,  pox  is  a  serious 
disease  in  the  State.  The  same  trouble  seems  also  to 
be  prevalent  in  Alabama,  where  it  was  recorded  by 
Wilcox  (114)  and  in  Oklahoma  as  reported  by  Learn 
(60).  The  disease  is  also  prevalent  In  Kansas,  Prof. 
L.  E.  Melchers  having  recently  sent  specimens  of  it  to 
the  writer. 

Name  of  the  Disease.  The  term  "soil  rot"  given  by 
Halsted  (27)  is  appropriate  only  in  so  far  as  it  indicates 
that  infection  takes  place  on  the  underground  portion  of 
the  plant.  It  suggests  practically  nothing  as  to  the  na- 
ture or  symptoms  of  the  disease.  In  New  Jersey  the 
trouble  is  known  to  growers  of  sweet  potatoes  as 
"ground  rot,"  a  name  not  more  suggestive  than  "soil 
rot."  In  Delaware  the  nature  of  the  disease  was  only 
vaguely  understood;  hence,  It  was  variously  known  as 
"bug  sting,"  "worm  hole,"  "fertilizer-burn,"  or  often 
mistaken  for  black  rot.  In  Texas  the  disease  has  no 
definite  name,  but  it  Is  variously  confused  with  the  many 
root  troubles  of  the  sweet  potato.  In  Virginia  the  disease 
is  known  to  growers  as  "pox,"  or  "pit,"  which  best  de- 
scribes the  trouble,  and  which  name  was  adopted  first  by 
the  author  (96)  and  later  by  Elliott  (18). 

Symptoms.     In  the  literature,  pox,    or   soil   rot,   is 


^ 

-rtr 

e 

...  "< 

^f 

¥^W-^i>^ 


W  %.  0 


^^^ 


Fig. 


Sweet  Potato  Pox. 


a.  Sweet  potato  root  badly  disfigured  by  pox.  /;.  Showing  cracking  of  the 
pox  spots  just  before  they  drop  out.  c.  Young  sweet  potato  roots  attacked 
by  pox.  d.  vSweet  potato  plant  with  rootlets  destroyed  by  pox.  e.  Cysts  of 
Cystospora  batata.  /.  Young  plasmodia  {e  and /after  Elliott),  g.  Stages  of 
Cystospora  batata  mistaken  bv  Halsted  for  a  fungus,  Acrocvstis  batatas  {aiter 
Halsted). 


Losses  from  Sweet  Potato  Diseases    109 

poorly  described,  the  symptoms  of  the  disease  not  being 
fully  given.  The  author's  extended  field  observations 
on  the  symptoms  of  pox  may  be  summarized  as  fol- 
lows: In  badly  affected  fields  the  stand  will  be  some- 
what uneven.  This,  however,  may  not  always  be  the 
case.  That  which  attracts  the  attention  most  is  thin 
growth,  stunted  vines,  and  a  pale-green  color  of  the 
foliage,  all  of  which  give  the  impression  of  a  very  im- 
poverished soil.  In  fact,  growers  do  not  attribute  these 
conditions  to  the  disease,  but  to  a  lack  of  certain  ele- 
ments in  the  soil  which  past  sweet  potato  crops  have  re- 
moved. Such  claims  are  unfounded,  as  these  soils  seem 
to  produce  good  crops  of  corn,  watermelons,  etc.  In 
pulling  out  a  sweet  potato  hill  from  a  soil  of  this  char- 
acter one  will  be  surprised  to  find  almost  no  secondary 
feeding  rootlets  (Fig.  7,  d).  This  is  especially  true 
when  the  examination  is  made  at  the  season  of  maxi- 
mum growth.  Many  of  the  feeding  rootlets  will  be 
found  totally  destroyed,  while  others  will  exhibit  nu- 
merous brownish  spots  at  various  intervals.  Generally 
speaking,  if  infection  starts  at  the  tip  of  a  growing  root, 
the  disease  will  work  its  way  upward,  and  destroy 
it  completely,  leaving  a  discarded  stub,  which  re- 
sembles the  infected  roots  of  other  crops  subject  to  the 
attacks  of  species  of  Thielavia.  On  the  other  hand,  if 
infection  takes  place  laterally,  the  resulting  spot  will  be 
limited  to  about  i/io  inch  (Fig.  7,  b  and  c).  Frequently 
such  roots  may  exhibit  5  to  10  spots,  each  separated 
from  the  others  by  a  healthy  area.  The  color  of  the 
spot  is  a  deep  chocolate-brown.  Such  infected  rootlets, 
it  is  needless  to  say,  become  fimctionless.  Besides  at- 
tacking the  feeding  rootlets,  the  pox  also  attacks  the 
small  roots  which  are  destined  to  develop  into  edible 
roots  (Fig.  7,  c).    This  infection  may  be  as  severe  and 


no  The  Sweet  Potato 

of  the  same  character  as  in  the  feeding  rootlets.  Re- 
duction in  yield,  lack  of  the  normal  green  color,  and 
limited  vine  growth  may  therefore  be  directly  attributed 
to  the  destruction  by  the  disease  of  the  feeding  rootlets 
and  young  roots. 

Infection  of  the  older  growing  roots  may  result  in  a 
constriction.  Growth  may  seem  to  cease  at  this  point, 
although  it  is  uninterrupted  on  either  side  (Fig.  7,  a). 
Infection  of  the  older  roots,  besides  misshaping  them, 
does  not,  however,  result  in  a  total  loss.  Such  roots 
usually  attain  a  fair  marketable  size,  and  do  not  suffer 
in  the  least  in  edible  quality.  Here,  however,  the  disease 
is  manifested  differently  from  that  on  the  young  root- 
lets.   On  the  older  roots  infection  may  be  of  two  types. 

The  normal  and  typical  one  is  characterized  by  small, 
dry,  darkish,  circular,  more  or  less  superficial  spots  the 
size  of  a  dime  or  smaller.  Later,  the  tissue  of  the  spot 
in  most  cases  dries  up,  cracks  (Fig.  7,  b),  and  falls  out, 
leaving  a  pox,  or  pit,  whence  the  name  of  the  disease. 
As  a  rule,  a  new  skin  is  formed  immediately  below  the 
area  of  the  fallen  spot.  The  depth  of  the  spot  seems  to 
vary  with  the  weather  conditions;  in  dry  weather  the 
pox  spots  seem  to  enter  more  deeply  into  the  tissue  than 
during  wet  spells.'  In  cases  of  light  infection,  there 
may  be  but  i  to  3  spots  on  the  potato.  In  severe 
cases,  however,  the  spots  may  be  so  numerous  as  to 
coalesce.  The  dead  tissue  of  the  spots  when  dropping 
out,  leaves  a  large,  ragged,  irregular  pit.  The  tissue  of 
the  pox  spot  is  dry  and  leathery,  but  is  readily  pulverized 
when  rubbed  between  the  fingers. 

The  second  form  of  infection  of  the  older  potatoes  is 
what  Elliott  (19)  terms  "blister"  infection.  It  was 
observed  by  the  author  but  once,  and  in  that  case  the  in- 
fection took  place  at  a  feeding  rootlet,  then  worked 


Losses  from  Sweet  Potato  Diseases     iii 

down  to  the  main  root,  and  was  later  apparent  as  a 
blister-like  elevation  on  the  epidermis. 

Methods  of  Spread.  It  has  already  been  stated  that 
in  dry  weather  the  pox  spot  seems  to  be  deeper  than  in 
wet  weather.  It  is  the  general  opinion  of  Halsted  (27), 
Townsend  (107),  and  Duggar  (15),  that  pox  is  worse 
during  dry  weather.  This  in  reality  is  true  only  in  so 
far  as  the  pox  spots  are  deeper,  and  cause  much  more 
visible  damage  by  distortion  and  disfigurement  of  the 
marketable  roots.  In  wet  weather  pox  is  just  as  severe, 
and  the  causal  organism  perhaps  more  active,  but  the 
spots  are  shallower  and  less  noticeable.  The  roots  are 
not  so  disfigured,  and,  hence,  are  more  saleable.  Ac- 
cording to  Halsted  {2^)  and  others,  pox  is  spread  about 
from  field  to  field  by  wind-blown  spores  of  the  causal 
organism.  The  work  of  the  author  does  not  seem  to 
bear  this  out.  Extended  observations  and  studies  have 
shown  that  pox  does  not  spread  readily  by  means  of 
wind-blown  spores  from  field  to  field  or  even  to  adjoin- 
ing fields.  If  it  did,  the  disease  would  spread  very  rap- 
idly over  large  areas.  This,  however,  is  not  the  case. 
Pox  will  not  become  very  noticeable  until  8  or  10  years 
after  its  introduction  in  a  field,  and  then  only  when  the 
crop  is  continually  grown  on  the  same  land.  The  disease 
does  not  seem  to  spread  rapidly  from  an  infected  field 
to  the  neighboring  field,  but  advances  slowly,  unnoticed 
and  unsuspected.  Definite  evidence  is  also  lacking  as  to 
whether  pox  is  carried  over  on  the  small  potatoes 
(seeds)  in  storage.  As  a  rule,  sweet  potato  growers 
never  hesitate  to  plant  infected  stored  seed.  According 
to  the  author's  observation,  and  numerous  communica- 
tions from  growers,  sprouts  from  such  seed,  when 
pulled  for  transplanting,  have  not  shown  evidences  of 
pox  on  any  of  the  underground  portions  of  the  plant. 


112  The  Sweet  Potato 

This  is  further  strengthened  by  Duggar  (15),  who 
states  that  "soil  rot  has  not  been  observed  to  spread  by 
way  of  the  hot-bed,  but  only  through  contamination  of 
the  soil  of  the  field."  In  order  to  verify  this,  the  author 
has  often  planted  infected  seed  which  wintered  over  in 
storage  in  a  sterilized  soil.  At  no  time,  however,  did 
the  resulting  sprouts  show  any  marks  of  pox.  The 
mode  of  spread  of  pox  needs  further  careful  investiga- 
tion. It  seems  reasonable  to  suppose,  however,  that  the 
disease  is  probably  disseminated  by  lumps  of  soil  which 
have  been  carried  on  farm  implements  on  wet  days, 
when  the  sandy  soil  is  more  likely  to  stick  together.  It 
is  also  likely  to  spread  from  diseased  sprouts  which  have 
been  grown  in  a  seed  bed,  the  soil  of  which  has  been 
taken  from  a  previously  infected  field.  Washing  by  rain 
is  also  likely  to  carry  the  disease  in  the  field.  In  lands 
with  a  natural  slope,  pox  will  be  seen  to  spread  down- 
ward in  the  direction  of  the  waterfall;  that  is,  from 
the  highest  to  the  lowest  point,  but  seldom  in  the  oppo- 
site direction. 

The  Organism.  That  Cystospora  batata  is  the  cause 
of  pox  has  been  amply  proved  by  Elliott  (18)  and  by 
the  author  ( 100) .  The  gross  morphology  of  Cystospora 
batata  has  already  been  indicated  by  Elliott  (19).  The 
organism  must  undoubtedly  hibernate  in  the  soil  as 
cysts.  This  stage  probably  enables  it  to  resist  drouth 
and  cold.  Careful  experiments  have  shown  that  freez- 
ing will  not  affect  C.  batata  in  infected  soil.  Pox-sick 
soil  in  flowerpots,  exposed  to  outdoor  freezing  weather 
during  the  entire  winter  will  not  show  the  least  weaken- 
ing in  the  virulency  of  the  causal  organism.  Similarly, 
ordinary  drying  of  the  soil  in  the  greenhouse  for  12 
months,  will  have  no  injurious  effect  on  C,  batata  in  the 
infected  soil. 


Losses  from  Sweet  Potato  Diseases     113 

The  cysts  (Fig.  7,  e  and  f  J  are  heavy-walled,  and 
each  individual  may  contain  large  numbers  of  swarm 
spores  or  amoebae.     When  the   latter   are   ready   to 
emerge,  the  cyst  wall  becomes  thinner,  until  finally  the 
swarm  spores  break  through.  Infection  of  the  host  may 
take  place  by  the  penetration  of  individual  amoebae  into 
the  epidermal  host  cells.    This  is  especially  the  case  with 
root  tips.    Ordinarily,  however,  infection  is  by  means  of 
a  Plasmodium  or  by  both  methods.    The  swarm  spores 
are  round,  but  slightly  tapered  at  both  ends,  and  possess 
a   single,    short   flagellum.      Occasionally   the    swarm 
spores  fuse  in  pairs,  but  from  the  author's  observations 
this  does  not  seem  the  rule.     They  are  usually  active 
after  emergence  from  the  mother  cyst.     The  period  of 
activity,  although  varying  from  i  to  7  days,  is  usually 
short,  often  less  than  30  minutes.     They  gradually  in- 
crease in  size,  taking  on  the  amoeboid,   then  the  plas- 
modial  form.    At  this  stage  a  large  number  of  nuclei 
are  formed  by  mitotic  division.  Nuclear  division  seems  to 
proceed  by  a  definite  mathematical  ratio  of  i,  2,  4,  8,  etc. 
Single  Plasmodia  may  often  contain  200  to  300  nuclei. 
At  this  stage  and  before  escaping,  the  Plasmodium  be- 
comes more  dense  and  thickly  granular  in  the  center, 
surrounded  by  a  clearer  zone  which   later  becomes   a 
thick  cell  of  the  cyst.    The  latter  apparently  undergoes 
a  short  period  of  rest,  during  which  time  the  swarm 
spores  are  formed.    These  in  turn  emerge  and  undergo 
the  same  life  cycle  as  above  described.     Thus,  in  a 
single  infected  root  tip  or  in  a  pox  spot,  several  crops 
of  swarm  spores  may  be  formed  within  the  host  cells, 
each  generation  of  which  advances  farther.    Finally  all 
the  Plasmodia  seem  to  collect,  cease  advancing,  turn 
outwards,  and  leave  the  pit  for  the  soil.     It  is  prob- 


114  The  Sweet  Potato 

able  that  the  plasmodia  in  the  soil  encyst  and  pass  the 
winter  in  that  way. 

In  describing  pox  (soil  rot)  Halsted  {2y)  has  figured 
a  new  fungus  of  a  new  genus  and  species,  which  he 
named  Acrocystis  batatas  E.  and  Hals.  The  latter  was 
practically  the  only  described  species  of  the  genus  Acro- 
cystis. However,  Halsted's  drawings  of  Acrocystis  are 
really  mistaken  figures  (Fig.  7,  g)  for  Cystospora 
batata,  a  myxomycete,  and  not  a  fungus.  It  has  been 
proved  that  pox  of  the  sweet  potato  is  caused  by  a 
myxomycete,  Cystospora  batata  Elliott.  It  is  therefore 
evident  that  Acrocystis  batatas  does  not  exist  at  all,  and 
that  the  genus  Acrocystis  is  not  valid. 

Other  Crops  Susceptible  to  Pox.  As  will  be  seen  pres- 
ently, pox  attacks  not  only  the  sweet  potato  but  other 
hosts  as  well.  In  the  summer  of  1914  an  old  Virginia 
grower  stated  to  the  author  that  he  never  plants  white 
(Irish)  potatoes  {Solanum  tubersoum)  on  the  same 
land  where  sweet  potatoes  affected  with  pox  have 
grown,  for  the  white  potato,  too,  is  subject  to  the  same 
disease.  Upon  further  inquiry  it  was  found  that  the 
same  practice  was  observed  by  most  growers  there. 
Bearing  this  in  mind,  in  1915,  Irish  potatoes  were 
planted  side  by  side  with  sweet  potatoes  in  a  field  badly 
infected  with  pox.  Observations  were  made  from  time 
to  time  by  pulling  out  growing  plants.  Unmistakable 
symptoms  of  the  pox  were  noticed  at  a  very  early  stage. 
At  harvest,  about  60  per  cent  of  the  tubers  of  the  Irish 
potato  were  affected  with  pox.  The  pox  spots  on  the 
Irish  potato  seemed  to  be  more  shallow.  Potato  grow- 
ers in  Virginia  maintain  that  some  varieties  of  Irish 
potatoes  seem  to  be  more  resistant  to  pox  than  others. 
The  Irish  Cobbler  is  apparently  least  resistant.  This 
statement  is  worthy  of  further  investigation.    That  pox 


Losses  from  Sweet  Potato  Diseases     115 

is  a  serious  disease  of  the  Irish  potato  there  seems  no 
doubt.  It  is  found  in  abundance  in  Virginia  and  is 
often  mistaken  for  common  scab. 

Elliott  (19)  too,  has  recorded  the  Irish  potato  as  a 
host  to  pox.  There  seems  no  doubt  that  the  disease  on 
the  Irish  potato  is  far  more  widespread  than  has  here- 
tofore been  recognized;  it  is  very  probable  also  that  it 
has  been  mistaken  and  confused  with  other  troubles. 
Morse  and  Shapovalov  (71)  and  more  recently  Ram- 
sey (83)  in  their  work  on  the  disease  caused  by  Rhizoc- 
tonia  sp.,  have  noticed  a  pitting  disease  of  the  Irish  po- 
tato that  has  been  attributed  to  that  fungus.  No  doubt 
Rhizoctonia  sp.  is  abundant  in  these  pits,  but  from  the 
illustrations  given  by  Morse  and  Shapovalov  it  is  evi- 
dent that  they  were  dealing  with  the  pox,  and  that  the 
trouble  caused  by  species  of  Rhizoctonia  was  merely 
secondary. 

Elliott  (19)  and  the  writer  (100)  have  already  stated 
that  the  pox  spots  on  the  Irish  potato  are  of  a  shallow 
type ;  however,  under  Maine  conditions,  it  is  very  prob- 
able that  Rhizoctonia  sp.  merely  enters  as  a  result  of 
the  injury  caused  by  Cystospora  batata,  and  that  having 
once  penetrated,  it  is  capable  of  working  in  farther,  thus 
deepening  the  pit.  Prof.  Ramsey  was  kind  enough  to 
send  the  writer  slides  of  his  so-called  "Rhizoctomia 
pits.**  In  every  case  these  slides  were  sections  of 
cracked  "pits."  A  careful  examination  showed  a  few 
remaining  cysts  irregularly  scattered  in  the  tissue  of  the 
"pit"  area.  Furthermore,  the  largest  quantity  of  fila- 
ments of  Rhizoctonia  sp.  were  found  in  the  center,  and 
at  each  side  of  the  crack  of  the  "pit"  was  a  place  from 
which  the  invading  Plasmodium  migrated  back  to  the 
soil.  It  seems  very  probable  that  the  growth  of  Rhizoc- 
tonia sp.  in  the  "pits"  is  limited  by  the  secretion  of  a 


Ii6  The  Sweet  Potato 

toxin  which  the  Plasmodium  of  C.  batata  leaves  in  the 
occupied  cells  before  migrating. 

Pox  on  the  Irish  potato  has  so  far  been  found  to  at- 
tack the  tubers  only,  and  not  the  roots  and  rootlets,  as  it 
does  with  the  sweet  potato.  Infection  apparently  takes 
place  at  a  lenticel,  as  Ramsey  also  found. 

The  turnip  (Brassica  rapa)  is  also  susceptible  to  pox. 
In  the  summers  of  1916  and  191 7  the  author  sowed 
turnip  seed  in  soil  infected  with  Cystospora  batata,  from 
which  sweet  potatoes  had  been  badly  diseased.  A  large 
percentage  of  the  turnips  showed  unmistakable  pox  in- 
fection. Here,  however,  the  spots  were  more  superficial 
than  or^  the  Irish  potato.  It  is  now  suspected  that  the 
beet  {Beta  vulgaris)  and  tomato  (Lycopersicon  esculen- 
tum)  are  also  subject  to  the  attack  of  this  disease. 

An  Actinomyces  Associated  zvith  Pox.  Of  the  many 
bacteria  and  fungi  isolated  from  pox,  a  species  of 
Actinomyces  is  very  often  obtained  from  diseased  spots. 
Inoculation  experiments  with  pure  cultures  of  this  or- 
ganism showed  that  it  is  capable  of  producing  a  spot 
which,  although  not  resembling  pox,  may  penetrate 
equally  deep  in  the  host  tissue.  This  species  of  Acti- 
nomyces was  isolated  from  sweet  potato  material  in 
Delaware,  as  well  as  from  specimens  grown  in  Texas. 
Cultures  of  the  organism  were  made  on  various  media, 
and  parallel  with  a  strain  of  Actinomyces  chromogenus 
from  the  Irish  potato,  secured  through  the  kindness  of 
Dr.  W.  J.  Morse,  of  the  Maine  Experiment  Station. 
The  two  organisms  appeared  to  be  distinct,  and  it  was 
thought  that  the  species  of  Actinomyces  grown  on  the 
sweet  potato  was  a  new  one,  to  which  the  name  Ac- 
tinomyces poolensis  Taub.  was  given. 

The  sweet  potato  Actinomyces  possesses  strong  pro- 
teolytic activities,  which  may  perhaps  serve  as  a  clue  to 


Losses  from  Sweet  Potato  Diseases    117 

its  pathogenicity.  The  cultural  earmarks  of  this  or- 
ganism are  as  follows : 

A  very  good  growth  is  produced  on  different  organic 
media  and  also  on  synthetic  media  containing  glucose 
or  glycerine.  A  good,  but  uncharacteristic  growth  was 
produced  on  Lubenau's  Qgg  medium,  Petroff's  medium, 
glycerine,  beef -infusion  agar,  and  Loeffler's  blood  serum. 
Growth  restricted,  cream-colored,  aerial  mycelium  gray 
to  musty-gray  on  Krainsky's  Ca-Malate  agar;  thin 
cream-colored  growth,  surface  becoming  covered  with 
an  ash-gray  aerial  mycelium,  on  Czapek's  solution  agar, 
in  which  glucose  or  glycerine  took  the  place  of  sucrose: 
the  growth  is  heavy,  yellowish,  aerial  mycelium  abund- 
ant, gray  or  white.  No  soluble  pigment  is  produced  on; 
any  of  the  media  studied.  On  potato  plug  the  growth  is 
light  brown,  no  aerial  mycelium  is  produced,  plug  is  not 
colored.  Milk  at  37  degrees  C.  is  hydrolized  in  15  days. 
Gelatine  at  15  degrees  C.  is  slowly  liquefied  (10  mm.  in 
20  days),  with  no  color  production  in  the  liquefied  por- 
tion ;  the  growth  is  light  brown,  with  no  aerial  mycelium. 
On  glucose  broth  a  flocculent  uncharacteristic  growth  is 
produced.  The  organism  grows  very  readily  on  all  the 
media  at  37  degrees  C. 

Microscopically  the  following  points  are  to  be  noted : 
Spirals  are  not  produced;  the  aerial  mycelium  soon 
breaks  up  into  short  cylindrical  spores,  although  many 
spherical  spores  are  found. 

Actinomyces  poolensis  is  a  superficial  wound  parasite, 
usually  found  following  the  pox  spots  produced  by 
Cystospora  batata.  The  former  organism  will  not  grow 
on  healthy  tubers  of  the  Irish  potato.  Structurally  A. 
poolensis  and  A.  chromogenus  differ  very  little.  They 
can  be  distinguished  only  pathologically  and  when 
grown  parallel  on  different  media. 


ii8  The  Sweet  Potato 

Methods  of  Controlling  Pox.  Halsted,  in  his  exten- 
sive field  work  on  the  control  of  pox,  found  that  a 
broadcast  application  of  300  or  400  pounds  per  acre  of 
both  sulphur  and  kainit  would  decrease  the  disease  and 
also  increase  the  yield  of  marketable  potatoes.  From  a 
practical  point  of  view  it  was  necessary  to  ascertain 
whether  an  alkaline  or  an  acid  fertilizer  would  favor  or 
control  pox  in  the  field.  Accordingly  an  infested  field 
that  had  been  chosen  received  a  normal  application  of 
1,000  pounds  per  acre  of  a  potash  phosphate  with  the 
following  guaranteed  analysis:  Ammonia  6  to  8  per 
cent,  available  acid  phosphate  7  to  8  per  cent,  potash 
5  per  cent.  The  land  was  then  divided  into  three  plots. 
The  middle  remained  as  a  check  and  received  no  further 
treatment.  The  plot  to  the  right  received  an  additional 
application  of  acid  phosphate  (guaranteed  analysis,  14 
per  cent  of  available  phosphoric  acid)  at  the  rate  of 
2,000  pounds  per  acre.  The  plot  to  the  left  received  an 
additional  application  of  hydrated  lime  (guaranteed 
analysis,  65  per  cent  of  calcium  oxid)  at  the  rate  of 
2,000  pounds  to  the  acre.  The  results  obtained  were 
very  striking.  The  control  plot  gave  an  average  of  al- 
most 60  per  cent  affected  roots.  The  lime  plot  in- 
creased the  amount  of  affected  roots  to  about  85  per 
cent.  The  percentage  of  diseased  roots  in  the  acid 
phosphate  plot  was  32.  This  seemed  to  indicate  that  an 
acid  fertilizer  has  a  tendency  to  keep  the  pox  in  check, 
whereas  lime  has  the  opposite  effect. 

Considerable  differences  seem  to  exist  in  the  resist- 
ance of  varieties  of  sweet  potatoes  to  the  disease.  Of  the 
limited  number  tested  in  19 15  in  Delaware,  the  follow- 
ing is  a  tentative  classification  of  their  resistance:  (a) 
apparent  total  freedom  from  disease  (Dahomey,  Red 
Brazil,  Pearson)  ;  (b)  from  i  to  20  per  cent  infected 


Fig.  8.     Slime  Mold. 

a.  Sweet  potato  leaf  and  petiole  covered  with  slime  mold  Phy- 
sariini  plumlwuni.  b  and  c.  Plants  covered  with  slime  mold,  Fuligo 
inolticen.  d.  White  rust.  e.  Cross-section  of  leaf  to  show  sorus  of 
spores  of  Cystiipiis  ipomoeae  pandurdnne. 


Losses  from  Sweet  Potato  Diseases     119 

(Big  Stem  Jersey,  White  Yam,  Yellow  Strassberger) ; 
(c)  from  20  to  90  per  cent  infected  (Goldskin,  Big 
Leaf,  Upriver). 

Steaming  the  soil  for  six  hours  at  20  pounds  pressure 
will  free  it  from  the  pox  organism.  This  also  seems  to 
be  true  when  the  infected  soil  is  treated  with  formalde- 
hyde at  the  rate  of  i  pint  in  20  gallons  of  water,  ap- 
plied at  the  rate  of  i  gallon  of  the  solution  to  each 
square  foot  of  soil  space.  However,  since  it  is  very 
doubtful  if  the  disease  is  carried  with  the  seed  in  the 
soil  of  the  seed  bed,  soil  sterilization  would  hardly  seem 
warranted  unless  it  aimed  also  at  controlling  black  rot. 
Likewise  it  seems  hardly  necessary  to  treat  the  seed  for 
that  alone.  It  is  not  definitely  known  how  long  Cys- 
tospora  batata  would  persist  in  the  soil  without  a  suit- 
able host.  Observations  of  practical  growers  differ 
greatly  in  this  respect.  Some  assert  that  at  least  a  10- 
year  rotation  is  necessary  to  free  the  land  from  pox; 
others,  and  these  seem  to  be  in  the  majority,  maintain 
that  a  3-year  rotation  is  sufficient.  Soil  conditions,  it 
seems,  are  an  important  factor.  Pox  is  more  severe 
in  the  lightest  of  the  sandy  soils,  and  less  so  in  the  heavy 
clay  loams. 

Powdery  Slime  Mold 

Caused  by  Fuligo  violacea  Pers. 

Frequently,  the  plants  in  sweet  potato  hot-beds  are 
covered  with  a  thick  slimy  growth  (Fig.  8,  b  and  c), 
which  is  at  first  soft  and  a  dirty  white,  gradually  be- 
coming yellowish,  and  when  mature  purple.  This 
growth  readily  breaks  up  at  the  least  touch  and  liberates 
a  copious,  purplish  powder  which  consists  of  the  spores 
of  the  organisms.    The  slimy  growth  appears  in  patches 


120  The  Sweet  Potato 

of  various  sizes,  ranging  from  a  quarter  of  an  inch  to 
three  feet  in  dimensions.  The  causal  organism,  Fuligo 
violacea  Pers.,  is  not  a  parasite  as  it  lives  only  super- 
ficially on  all  the  exterior  parts  of  the  plant.  How- 
ever, when  the  leaf  stomata  are  covered  so  as  to  shut 
out  the  light,  the  general  effect  is  that  of  suffocation, 
since  plants  thus  affected  become  yellow  and  languid 
and  look  messed  up. 

Another  slime  mold  organism,  Physarum  plumbeum 
Fries.,  also  occurs  on  sweet  potato  plants  in  hot-beds. 
However,  it  forms  no  lumpy  growth,  but  appears  as 
delicate,  star-shaped,  cup-like  incrustations  (Fig.  8,  a). 
Physarum  plumbeum  is  not  a  parasite;  it  lives  only 
superficially  on  the  petioles  and  foliage,  and  exerts  the 
same  indirect  harmful  effect  as  Fuligo  violacea. 

To  prevent  the  rapid  spread  of  the  above  slime  molds, 
infected  patches  should  be  carefully  removed  and  de- 
stroyed by  fire.  This  should  be  done  before  the  causal 
organisms  ripen  into  the  spore-bearing  stage.  Over- 
watering  and  insufficient  ventilation  will  favor  the 
growth  of  these  slime  molds,  which  are  seldom  met 
with  in  the  fields. 


White  Rust 

Caused  by  Cystopus  ipomoeae-panduranae  Pari. 

Distribution  and  Economic  Importance.  White  rust 
is  probably  found  wherever  sweet  potatoes  are  grown. 
It  has  been  observed  by  the  author  in  New  Jersey,  Dela- 
ware, Maryland,  Virginia,  Alabama,  Georgia,  Missis- 
sippi and  Texas.  Harter  (40)  has  also  seen  it  in  Iowa 
and  says  that  it  is  widely  distributed  there. 


Losses  from  Sweet  Potato  Diseases     121 

White  rust  Is  a  field  disease  which  attacks  foHage  and 
petioles  only ;  and  is  rarely  found  on  the  stem.  It  is  of 
little  economic  importance,  although  it  probably  causes 
indirect  losses  in  yields.  While  it  is  true  that  the  sweet 
potato  is  grown  only  for  its  roots,  nevertheless,  a  good 
crop  depends  on  healthy  and  abundant  foliage.  The 
sugar  and  the  starch  in  the  sweet  potato  are  not  manu- 
factured from  the  soil,  but  are  made  by  the  leaves  from 
the  air  and  then  stored  in  the  roots.  The  effect  of  white 
rust  in  killing  much  of  the  foliage  is  to  curtail  the 
amount  of  manufactured  sugar  and  starch  and  this  in 
turn,  no  doubt,  results  in  a  shorter  crop. 

Symptoms  of  the  Disease.  White  rust  appears  when 
the  plants  have  usually  made  good  vine  growth  and 
when  the  hills  are  beginning  to  set,  i.e.,  to  form  new 
sweet  potatoes  in  the  soil.  A  typical  symptom  of  white 
rust  then  is  the  yellowing  of  the  leaves  in  the  center  of 
the  plant,  which  later  turn  brown,  shrivel,  and  die. 

In  carefully  examining  the  center  leaves  as  they  begin 
to  yellow,  we  see  that  on  the  under  side  of  such  leaves 
there  are  many  minute,  white  raised  pimples  (Fig.  8, 
d  and  e),  each  of  which,  when  it  is  touched  with  the 
finger,  sheds  a  white  dust,  made  up  of  millions  of  spores 
of  the  fungus.  Each  white  pimple  on  the  under  side  of 
the  leaf  is  denoted  by  a  small  yellow  area  on  the  upper 
surface.  In  cases  of  mild  infection  there  are  usually 
few  pimples  on  a  leaf,  but  when  the  disease  is  severe, 
the  leaf  is  ,literally  peppered  with  them.  White  rust  is 
worse  when  the  weather  is  dry  and  the  nights  are  cool, 
and  it  is  more  abundant  in  the  shaded  portions  of  the 
field. 

The  Organism.  The  first  mention  of  the  white  rust 
organism  in  the  United  States  was  made  by  Halsted 
(27),  who  spoke  of  it  as  Cystopus  ipomoeae-panduranae 


122  The  Sweet  Potato 

Farl.  In  Saccardo  Sylloge  Fungorum  9:341,  an  or- 
ganism Cystopus  ipomeae-panduranae  (Schw.)  Stev.  et 
Sw.  Is  described  as  found  on  Ipomoeae  hederaceae, 
lacunosae,  leptoplyllae  et  panduranae.  In  1904,  Stevens 
(88)  adapted  the  generic  name  Albugo,  and  referred  to 
the  sweet  potato  organism  as  Albugo  ipomoeae-pan- 
duranae  (Schw.)  Sw.,  which  is  also  adopted  by  Harter 
(40)  and  others.  In  1909  Duggar  (17)  refers  to  Cys- 
toptis  convulvulacearum  Otth.,  which  is  also  mentioned 
in  Saccardo  Sylloge  Fungorum  9:340,  found  on  species 
of  Ipomoeae  gossypioidis.  In  this  connection,  Duggar 
(17)  states  that  Cystopus  convulvulacearum  is  also 
found  on  the  sweet  potato.  Harshberger  (52)  speaks 
of  the  white  rust  organism  as  Cystopus  ipomoeae  pan- 
duranae Farl. 

It  is  thus  seen  that  there  seems  to  be  considerable  con- 
fusion and  lack  of  agreement  as  to  the  proper  name.  It 
might  be  asked  if  Cystopus  ipomoeae-panduranae  Farl. 
is  the  same  as  Cystopus  ipomeae  panduranae  (Schw.) 
Stev.  et  Sw.  It  might  be  further  asked  if  Cystopus  con- 
vulvulacearum Otth.  is  the  same  or  similar  to  the  above 
two  mentioned. 

Host  Relationship.  Halsted  (27)  stated  that  Cysto- 
pus ipomoeae-panduranae,  the  cause  of  the  white  rust 
of  the  sweet  potato,  also  attacks  many  other  hosts  of 
the  morning  glory  family,  especially  the  wild  morning 
glory.  The  disease  on  this  latter  host  causes  large 
swellings  and  galls,  in  which  are  formed  the  oospores. 
Stevens  (91)  states  thsit  Albugo  (Cystopus)  ipomoeae- 
panduranae  (Schw.)  Stev.  et  Sw.  attacks  not  only  the 
sweet  potato  but  also  various  species  of  Convulvulaceae, 
such  as  the  morning  glory  and  the  moon  flower. 

In  191 5,  McClintock  (64)  was  unable  to  infect  sweet 
potato  plants  with  spores  from  the  wild  morning  glory 


Losses  from  Sweet  Potato  Diseases     123 

white  rust,  and  morning  glory  plants  with  spores  from 
the  sweet  potato  white  rust.  Spores  of  white  rust  from 
each  of  these  hosts,  however,  infected  healthy  plants  of 
its  respective  hosts.  Similar  tests  were  made  by  the 
author  in  19 16  and  191 7,  and  the  spores  of  the  white 
rust  from  the  sweet  potato  and  the  wild  morning  glory 
were  subjected  to  freezing  as  was  recommended  by 
Melhus  (68),  but  with  no  effect.  This  seems  to  indi- 
cate that  the  causal  organism  of  the  white  rust  of  sweet 
potatoes  is  probably  a  distinct  species  from  that  of  the 
wild  morning  glory.  The  symptoms  on  the  latter  are 
always  accompanied  by  swellings  or  large  galls  on  the 
blossoms,  foliage,  petioles,  and  stems.  Such  symptoms 
have  never  been  observed  by  the  author  to  occur  on  the 
sweet  potato. 

Control.  With  our  present  meagre  knowledge  of 
white  rust,  it  is  not  possible  to  formulate  definite  meth- 
ods of  control.  Crop  rotation  seems  to  be  no  factor  of 
importance.  The  disease  is  found  on  new  land  as  well 
as  on  land  where  sweet  potatoes  were  grown  several 
years  in  succession.  Of  the  thirty  varieties  grown  by 
McClintock  (64)  none  has  shown  to  be  entirely  im- 
mune. On  the  other  hand,  some  varieties  seemed  to  be 
slightly  more  resistant  than  others.  From  the  author's 
observations,  it  seems  that  the  Southern  Queen  variety 
possesses  considerable  immunity  to  the  white  rust.  High 
temperatures,  frequent  rains,  heavy  dews,  and  a  high 
relative  humidity  in  the  air  favor  the  spread  of  this 
disease. 


CHAPTER  IX 

specific  diseases 
Soft  Rot 

Caused  by  Rhizopus  nigricans  Ehr. 

"K  Field  Trouble.  Soft  rot  is  not  primarily  a  field 
disease;  however,  it  is  frequently  met  with  at  digging, 
causing  considerable  damage.  McClintock  (64)  re- 
ported a  serious  outbreak  in  Virginia  of  soft  rot  in  the 
field.  For  the  harvesting  of  the  sweet  potatoes  in  that 
state,  a  vine  cutter  made  from  a  disc  harrow  with  all 
but  two  discs  removed  is  generally  used.  In  cutting  the 
vines,  the  discs  penetrate  deeply  in  the  soil,  and  badly 
cut  and  bruise  many  of  the  potatoes,  which,  as  a  result, 
soft-rot  just  as  they  are  dug.  Uninjured  roots  in  the 
same  hill  remain  free  from  the  disease.  From  this  it 
seems  evident  that  the  cutting  of  the  vines  should  be 
done  at  the  time  when  the  potatoes  are  dug.  It  is  un- 
safe to  leave  injured  potatoes  (this  also  applies  to  pota- 
toes struck  by  frost)  in  the  ground  for  more  than  twelve 
hours.  Furthermore,  no  vine  cutter  should  be  used  that 
goes  in  the  soil  deep  enough  to  injure  the  roots. 

As  a  field  disease,  soft  rot  may  be  expected  in  heavy 
soils  with  poor  drainage,  and  during  prolonged  wet 
weather  before  or  during  harvesting.  The  disease  is 
especially  aggravated,  when,  during  harvesting,  a  plow 
is  used  that  bruises  or  injures  the  potatoes. 

As  a  Seed  Bed  Trouble.  Soft  rot  is  a  disease  which  is 
124 


Specific  Diseases  125 

often  met  with  in  the  hot-bed.  Here  the  potatoes  may 
rot  as  soon  as  they  are  bedded,  or  later  at  various  in- 
tervals. Soft  rot  in  the  hot-bed  is  favored  by  bedding 
bruised  potatoes  and  by  failure  to  disinfect  them  with 
corrosive  sublimate  (see  p.  24).  Sudden  rising  or  low- 
ering of  temperature,  over-watering,  poor  ventilation, 
walking  upon  and  trampling  the  roots  during  bedding  or 
when  drawing  sprouts  are  all  conducive  to  soft  rot  in 
the  hot-bed.  Care  exercised  in  these  directions  will  re- 
duce to  a  minimum  the  losses  from  soft  rot. 

As  a  Storage  Trouble.  The  seriousness  of  soft  rot  in 
storage  was  pointed  out  by  Halsted  (27),  and,  in  fact, 
by  all  writers  and  investigators  of  sweet  potato  diseases. 
In  Delaware,  the  author  (103)  estimated  about  30  per 
cent  loss  in  storage.  Wilcox  (114)  and  Carver  (8) 
state  that  soft  rot  is  one  of  the  worst  storage  diseases. 
The  conditions  which  favor  this  rot  indoors  are  the 
following : 

1.  Rough  handling,  bruising  the  potatoes  in  the 
field  while  harvesting,  hauling  and  filling  the  storage 
house. 

2.  Storage  of  potatoes  frosted  in  the  field. 

3.  Frosted  potatoes  due  to  a  loose  house,  sudden 
drop  of  temperature  or  lack  of  fire  in  the  house  dur- 
ing cold  weather. 

3.  Poorly  ventilated  house. 

4.  Overcrowded  house. 

5.  Overheating  and  lack  of  ventilation. 

6.  Frequent  handling  of  sweet  potatoes  during 
storage. 

Symptoms.  Soft-rotted  potatoes  are  at  first  soft  and 
mushy.  When  pressed  with  the  finger,  the  tissue  will 
readily  yield  and  break  open,    and   a  clear   brownish 


126  The  Sweet  Potato 

liquid  will  spill  out.  The  rot  usually  starts  from  either 
end  of  the  potato.  When  there  is  no  crack  on  the  root, 
it  will  merely  soft-rot,  gradually  shrink  (Fig.  9,  a), 
because  of  the  evaporation  of  its  interior  moisture,  and 
finally  dry  and  become  mummified.  When  the  potatoes 
are  taken  out  for  shipment,  the  dried  mummies  show 
no  evidence  of  previous  relationship  to  the  early  soft 
rot  stage  and  therefore  many  growers  do  not  recognize 
soft  rot  as  a  serious  storage  disease.  When  freshly 
soft-rotted  potatoes  are  cut  or  bruised,  the  causal  fun- 
gus, Rhizopus  nigricans,  will  send  out  its  fruiting  stalks 
and  resemble  a  whiskered  growth  (Fig,  9,  b).  When 
such  potatoes  are  placed  in  a  wire  basket  and  under  a 
closed  bell  jar,  the  Rhizopus  growth  with  its  fruiting 
stalls  will  overrun  the  potatoes  and  the  basket  (Fig. 
9,  d),  and  form  a  thick  matted  fungus  groAvth.  In  the 
bins,  the  presence  of  soft  rot  may  always  be  detected 
by  a  liquid  dripping  from  the  rotted  potatoes  and  wet- 
ting the  healthy  ones  nearby.  The  wetting  frequently 
favors  infection  of  the  neighboring  healthy  roots,  al- 
though this  does  not  always  occur. 

Odor  of  Soft  Rot.  Very  often  we  hear  storage  men 
accuse  the  soft  rot  of  emitting  strong  disagreeable  odors. 
Similar  statements  are  also  found  in  the  literature. 
Price  (80)  found  that  when  potatoes  are  attacked  they 
become  soft  and  worthless  and  give  off  an  offensive 
odor.  Starnes  (87)  too,  observed  that  the  entire  con- 
tents of  a  bin  may  be  reduced  to  a  pulpy  mass  of  cor- 
ruption, emitting  a  most  disgusting  odor.  Contrary  to 
general  belief,  soft  rot  in  the  bins  is  at  first  odorless  for 
a  week  or  ten  days.  After  that  time  acetic  fermenta- 
tion sets  in,  and  this  becomes  quite  noticeable.  It  seems 
that  this  odor  attracts  the  females  of  a  species  of  fruit 
fly  which  lay  their  eggs  in  the  rotting  potato.     At  this 


■■■^  'i  l'.^^   *:. 


•  'v  f. 


a 


b 


.mm 


Fig.  9.    Soft  Rot. 

a.  Sweet  potato  freshly  soft-rotted,  b  to  c?.  Soft-rotted  sweet  potatoes 
covered  with  the  fruiting  stalks  of  Rhizopus  nigricans  (after  Harter,  L.  L.). 
e.  Pure  culture  of  Rhizopus  nii^ricans  from  tissue  of  a  freshly  soft-rotted  sweet 
potato.  /.  Pure  culture  of  ()its(>ora  lactis  from  tissue  from  a  soft-rotted 
sweet  potato  20  days  old.  g.  and  /;.  Stages  in  zygospore  formation  of  R.  ttii^i-r. 
i.  Mature  zygospore. 


Specific  Diseases  127 

stage  badly  affected  storage  houses  are  literally  swarm- 
ing with  these  gnats.  The  acetic  fermentation  may  last 
for  a  week  or  ten  days.  After  that  time,  the  affected 
potatoes  have  partially  dried  out  and  fungi,  such  as 
Diaporthe  batatatis  (Hals.)  Hart.,  Fusarium  batatatis 
WoU.,  Sclerotium  bataticola  Taub.,  and  many  others 
may  gain  entrance.  It  sometimes  happens  that  putre- 
faction follows  the  acetic  fermentation.  Bacteria  are 
no  doubt  involved  in  this  process,  for  at  this  time  the 
affected  potato  is  fairly  putrid  and  the  odor  is  errone- 
ously attributed  to  soft  rot. 

The  Organism.  The  general  morphology  of  Rhizo- 
pus  is  well  known.  The  spore  germinates  easily  by 
sending  out  a  germ  tube  which  grows  and  branches 
rapidly,  forming  a  mat  of  mycelial  growth,  also  send- 
ing out  many  stolons.  On  these  stolons  are  borne  the 
sporangiophores  (Fig.  lo,  c  to  e).  The  latter  usually 
develop  at  the  base  of  origin  a  few  rhizoids  which  ac- 
cording to  Swingle  (94)  help  to  nourish  and  anchor  the 
organism.  Each  sporangiophore  bears  a  single  spheri- 
cal sporangium.  The  protoplasm  in  young  mycelium  is 
seen  to  be  slowly  streaming  (Fig.  10,  g).  The  cyto- 
plasm in  young  sporangia  is  densest  next  to  the  wall  and 
clearest  in  the  center.  The  formation  of  spores  begins 
when  the  columella  is  well  apparent.  The  spores  are  at 
first  angular  and  covered  by  a  thin  plasma-membrane. 
When  fully  ripe,  they  round  off  and  take  on  a  firm  wall. 
The  spores  are  set  free  by  the  bursting  of  the  sporan- 
gium wall  without  its  being  thrown  off.  The  mature 
spores  are  ovoid  in  shape  and  vary  in  size.  The  spore 
walls  are  marked  with  longitudinal  ridges  (Fig.  10,  f). 

The  development  of  sexual-resting  or  winter  spores 
(zygospores)  has  been  worked  out  by  Blakslee  (4). 
Hyphae  of  two  distinct  mycelia,  designated  as  -\-  and  — 


128  The  Sweet  Potato 

strains,  are  formed,  each  giving  rise  to  lateral  club- 
shaped  branches.  The  tips  of  these  branches  (gametes) 
come  together,  and  each  is  cut  off  from  its  original 
branch  by  a  transverse  wall.  The  contents  of  two 
gamete  cells  fuse,  and  the  result  is  the  resting  sexual 
spores  or  zygospore  (Fig.  9,  g  to  i).  The  latter  has  a 
thick,  warty,  brown  coat.  The  zygosporic  stage  seems 
to  play  no  important  role  in  the  life  cycle  of  Rhizopiis 
nigricans,  as  the  fungus  Is  carried  over  from  year  to 
year  through  its  sporanglospores  (Fig.  10,  f). 

Other  Hosts  of  Rhizopus  Nigricans.  Besides  on  the 
sweet  potato,  R.  nigricans  is  more  frequently  found 
growing  on  decayed  vegetables,  and  especially  on  moist 
bread,  whence  the  name  bread  mold.  According  to 
Halsted  R.  nigricans  also  produces  a  soft  rot  on  quince 
fruit. 

In  1909,  Orton  (75)  called  attention  to  a  decay  of 
the  white  or  Irish  potato  which  is  generally  known  as 
"leak"  or  "melters,"  and  which  he  attributed  to  Rhizo- 
pus nigricans  Ehr.  In  1909,  Morse*  mentioned  a  fruit 
rot  caused  by  a  species  of  Rhizopus.  Haslamf  found  the 
fungus  Rhizopus  nigricans  in  great  abundance  on  corn, 
apparently  causing  blind  staggers  in  horses.  EdgertonJ 
described  a  soft  rot  of  the  fig  which  he  attributed  to  the 
same  fungus.  He  claimed  in  some  cases  a  loss  of  more 
than  90  per  cent  of  the  fruits.  Stevens  and  Wilcox 
(92)  have  proven  that  R.  nigricans  causes  a  rot  of 
strawberries  In  transit.  In  Texas  it  causes  a  soft  rot  of 
squashes  in  the  field  as  well  as  in  storage. 

*  Morse,  W.  J.,  Notes  on  plant  diseases.  Maine  Agr.  Expt.  Sta. 
Bui.  164  :  1-28,  1909. 

t  Haslam,  T.  P.,  Meningo  Encephalitis  (blind  staggers).  Kansas 
Agr,  Expt.  Sta.  Bui.  173  :  235-251,  1910. 

X  Edgerton,  C.  W.,  Diseases  0}  the  fig  tree  and  fruit,  Louisiana  Agr. 
Expt.  Sta.  Bui.  126  :  5-20,  1911. 


Fig.  io.     Soft  Rot. 

a.  Artificially  inoculated  sweet  potatoes  with  spores  of  Rhizopus  nig^ricans; 
to  the  left,  chamber  kept  open  and  dry,  healthy;  to  the  right,  chamber 
kept  covered  and  moist,  soft-rotted,  h.  Same  as  a;  to  the  left,  kept  under 
bell  jar  on  receptacle  which  contained  sulj^huric  aciil,  the  latter  ab.sorbin^j; 
the  moisture  in  the  bell  jar,  healthy;  to  the  right,  no  sulphuric  acid,  soft- 
rotted,      c.  Group   of   sporangiophores  bearing  sporangia  of  R.  nigncuns. 

d.  Sporangium  of   R.  nigricans   in  which    the  spores  are  completely  iformed. 

e.  Young  sporangium  of  R.  nigricans,  f.  Ripe  spores  of  R.  nigricans. 
g.  Longitudinal  section  through  stolon  to  show  distribution  of  cytoplasm  in 
R.  nigricans  ic  to  i;  after  Swingle,  D.  B.). 


Specific  Diseases  129 

Life  History  of  Rhizopus  Nigricans.  Experiments 
by  the  author  have  shown  that  R.  nigricans  is  not  car- 
ried over  from  year  to  year  as  mycelium  in  the  soft- 
rotted  potatoes.  On  the  contrary,  after  the  disease  runs 
its  course,  the  fungus  within  the  tissue  begins  to  die  out 
gradually.  Cultures  were  made  of  the  fungus  from 
soft-rotted  potatoes  of  various  ages.  Each  day  when 
the  platings  were  made  (Fig.  9,  e),  two  infected  roots 
were  used  at  a  time.  Nearly  the  entire  content  was 
cultured,  making  a  total  of  thirty  to  fifty  poured  plates 
each  day.  From  the  ninth  to  the  twelfth  day,  the 
Rhizopus  fungus  was  seen  to  lose  rapidly  in  vigor.  At 
this  stage,  the  platings  yielded  a  very  weak  growth  of 
Rhizopus  followed  by  species  of  Oospora  lactis  (Fres.) 
Sacc.  and  Oosporoidea  lactis  (Fres.)  Sums  (Fig.  9,  f), 
respectively.  By  the  twelfth  to  the  fifteenth  day,  the  fun- 
gus R.  nigricans  had  disappeared  completely  and,  instead, 
pure  cultures  of  Oospora  lactis  and  Oosporoidea  lactis, 
as  well  as  putrefying  bacteria,  took  its  place.  By  the  fif- 
teenth to  the  twenty-fifth  day  the  above  two  fungi  had 
gradually  disappeared,  giving  place  to  more  colonies  of 
bacteria,  several  species  of  Fusaria,  Trichoderma  Ko- 
ningi  Oud.,  Nectria  ipomoeae  Hals,  and  several  others. 
Microscopic  examination  of  crush  mounts,  on  the  respec- 
tive dates  when  the  platings  were  made,  revealed  some 
very  interesting  facts.  During  the  first  week,  when  the 
infected  roots  yielded  pure  cultures  oi  R.  nigricans,  the 
hyphae  under  the  microscope  were  hyaline  and  the  pro- 
toplasmic granules  very  even.  As  the  fungus  gradually 
began  dying,  the  mycelium  as  well  as  the  protoplasmic 
granules  turned  brown.  Many  filaments  too  were  found 
empty  and  shriveled,  altogether  Indicating  actual  death 
of  the  fungus.  It  was  further  observed  in  studying  the 
crush  mounts,  that  the  fungus  in  the  host  tissue  is  both 


130  The  Sweet  Potato 

inter-  and  intra-cellular.  The  middle  lamella  of  the  cells 
are  in  most  cases  dissolved  and  the  starch  grains  cor- 
roded. This  is  no  doubt  the  result  of  enzyme  action. 
Harter  and  Weimer  (41,  47  and  no)  have  found  that 
Rhizopus  tritici  Saito  is  capable  of  destroying  the  sweet 
potato  through  powerful  enzymic  action. 

Susceptibility  of  Sweet  Potatoes  to  Rhisopus.  Work 
done  by  Harter  and  Weimer  (49)  showed  the  follow- 
ing: I.  Very  susceptible  varieties  include,  Gold  Skin, 
Little  Stem  Jersey,  Georgia,  Early  Carolina,  Red 
Brazil,  Haiti,  Yellow  Belmont  and  Dooley.  2.  Very 
resistant  varieties  of  which  may  be  mentioned  Southern 
Queen  and  Nancy  Hall.  3.  Intermediate  varieties  such 
as  Porto  Rico,  Big  Stem  Jersey,  Triumph,  Pierson, 
Florida  and  Dahomey. 

Storage  Conditions  Which  Favor  Soft  Rot.  Since 
soft  rot  is  a  very  serious  storage  disease,  it  Is  necessary 
to  determine  what  if  any  indoor  conditions  particularly 
favor  its  spread.  Extended  studies  and  observations  by 
the  author  in  over  three  hundred  sweet  potato  storage 
houses  have  indicated  that  stagnant  moisture  and  poor 
ventilation  are  both  unfavorable  to  sweet  potatoes.  A 
minimum  of  soft  rot  is  found  in  storage  houses  which 
are  provided  with  ample  means  of  ventilation.  Less  soft 
rot  is  also  found  in  those  houses,  where  the  relative 
humidity  of  the  indoor  air  seldom  rises  above  70  per 
cent.  Through  properly  constructed  houses  this  condi- 
tion is  attained. 

In  order  to  determine  the  effect  of  moisture  on  soft 
rot,  the  following  simple  experiments  were  carried  out: 

Moisture  Experiment  with  Crude  Sulphuric  Acid. 
Bell  jars  were  used  to  cover  wire  baskets  (Fig.  10,  b) 
5X5X5  Inches  containing  sound  sweet  potatoes.  These 
were  kept  in  the  laboratory  one  week  to  determine  the 


Specific  Diseases  131 

presence  or  absence  of  soft  rot  infection.  Crude  sul- 
phuric acid  was  used  as  a  drying  agent,  being  placed  in 
flat  glass  dishes  5  inches  in  diameter  and  2  inches  deep. 
The  amount  of  acid  used  is  indicated  in  Table  23.  Two 
of  the  baskets  were  left  as  checks  without  the  drying 
agent;  the  remaining  six  were  subjected  to  the  acid. 
Duplicates  marked  A  and  B  in  Table  23  were  run  in  each 
experiment.  Before  being  covered  with  the  bell  jars, 
each  root  in  the  baskets  was  smeared  with  spores  from 
pure  cultures  of  R.  nigricans,  applied  with  a  camel's-hair 
brush.    The  results  obtained  are  given  in  Table  23. 

From  Table  23  it  is  seen  that  both  checks  were  in- 
fected with  soft  rot  the  third  day  of  the  experiment, 
giving  an  average  of  85  per  cent  infection.  Where 
100  cc.  of  sulphuric  acid  was  used,  infection  was  re- 
tarded from  twenty-three  to  thirty-eight  days,  and  the 
amount  of  infection  was  only  7  per  cent.  As  the  acid 
was  reduced  from  100  to  50  cc,  infection  was  retarded 
fifteen  or  sixteen  days,  and  increased  to  about  80  per 
cent.  As  the  acid  was  further  decreased  to  25  cc,  in- 
fection was  retarded  ten  or  eleven  days,  but  increased 
from  80  to  90  per  cent,  nearly  equalling  the  per  cent 
of  infection  in  the  checks.  It  is  evident,  therefore,  that 
the  more  acid  we  use,  the  greater  its  power  of  absorb- 
ing the  moisture  which  is  given  off  and,  therefore,  the 
greater  the  time  required  for  infection. 

Ring  Rot 

Caused  by  Rhizopus  nigricans  Ehr. 

Ring  rot  was  described  by  Halsted,  who  attributed 
its  cause  to  the  fungus,  Nectria  ipomoeae  Hals.  How- 
ever, the  author   (97)  has  definitely  proved  that  the 


132 


The  Sweet  Potato 


Table  23 
Effect  of  Drying  with  Sulphuric  Acid  on  Soft  Rot 


Kind  of  Treatment 


Checks 


100  cc.  Acid 


Weight  in  grams  of  sweet  pota 
toes  at  first  date  of  experi 
ment 

Weight  in  grams  of  same  at  end 
of  experimetit 

Date  of  inoculation 

First  date  of  infection 

Per  cent,  of  infection 

Amount  of  water  given  off  in 
grams 


1363 

1243 
Dec.  5, 

1912 
Dec.  8, 

1912 
90 

120 


1363 

1195 
Dec.  5, 

1912 
Dec.  8, 

1912 

80.85 

167 


1465 

1077 
Dec.  5, 

1912 
Jan.  12, 

1913 
7 

388 


1347 

1056 
Dec.  5, 

1912 
Dec.  28, 

1912 
•     7-7 

291 


Kind  of  Treatment 


50  cc.  Acid 


25  cc.  Acid 


Weight  in  grams  of  sweet  pota- 
toes at  first  date  of  experi- 
ment   

Weight  in  grams  of  same  at  end 
of  experiment 

Date  of  inoculation 

First  date  of  infection 

Per  cent,  of  infection 

Amount  of  water  given  off  in 
grams 


1363 

1 135 
Dec.  5, 

1912 
Dec.  20, 

1912 
83 

228 


1290 

1040 
Dec.  5, 

1912 
Dec.  21, 

1912 
80 

250 


1360 

1 132 
Dec.  5, 

1912 
Dec.  15, 

1912 
80 

228 


1307 

1090 
Dec.  5, 

1912 
Dec.  16, 

1912 
90 

217 


disease  is  induced  by  Rhizopus  nigricans,  the  cause  of 
soft  rot.    Like  soft  rot,  ring  rot  is  primarily  a  storage 


Fig.  II.     Ring  Rot. 

a.  Freshly   ring-rotted  sweet  potato  placed  in  a  mf)ist  chamber  overnight. 
Note  the  Rhizopus  growth  on  the  ringed  area.    b.  to/.  Various  forms  of  ring  rot. 


Specific  Diseases  133 

disease,  although  it  occurs  in  the  field  and  in  the  hot- 
bed. 

Symptoms.  Before  describing  the  symptoms,  it  must 
be  stated  at  the  outset  that  there  are  two  forms  of  ring 
rot,  both  of  which  are  stages  of  the  same  disease.  The 
first  stage  is  the  soft  ring.  This  is  characterized  by  a 
soft-rotted  area  which  girdles  the  root,  thereby  form- 
ing a  complete  ring.  This  ring  may  be  formed  in  the 
center,  at  the  tip  end,  or  at  any  part  of  the  root.  The 
formation  of  the  soft  ring,  like  soft  rot,  takes  place  as 
soon  as  the  sweet  potatoes  are  put  in  storage.  As  the  roots 
are  usually  stored  in  bulk  in  bins,  and  as  the  soft  ring, 
like  the  soft  rot,  is  confined  to  roots  more  or  less  deeply 
buried  in  the  bin,  the  disease  is  overlooked.  The  soft 
ring,  like  the  soft  rot,  is  at  first  odorless,  but  in  a  week 
to  ten  days  it  is  followed  by  a  characteristic  fermenta- 
tion. Fruit  flies  which  are  constantly  associated  with 
soft  rot  in  storage  are  also  associated  with  the  soft  ring. 
The  soft  ring  gradually  begins  to  dry  by  losing  the  water 
which  resulted  from  the  breaking  down  of  the  starch. 
The  drying  is  noticed  by  shrinkage  and  contraction  of 
the  entire  ringed  area,  forming  a  slight  groove  (Fig. 
II,  b  to  f).  In  two  to  six  weeks  the  ring  becomes  very 
dry  and  more  or  less  hardened,  varying  with  the  nature 
of  the  fungi,  which  act  as  secondary  invaders.  This  then 
brings  us  to  the  second  form  or  dry  ring  rot,  which  is 
nothing  more  than  the  last  stage  of  the  soft  ring  in 
which  the  primary  parasite  has  died  out  (Fig.  ii,  b). 

Proofs  that  Ring  Rot  and  Soft  Rot  Are  Both  Caused 
by  the  Fungus  R.  Nigricans  Ehr.  Ring  rot  is  similar  to 
soft  rot  except  that  in  the  former  the  decayed  area  is 
limited  to  a  ring. 

I.  Ring  rot,  like  soft  rot,  starts  when  the  sweet  pota- 
toes are  first  brought  into  storage. 


134  The  Sweet  Potato 

2.  In  fresh  ring  rot,  as  in  fresh  soft  rot,  the  fungus 
does  all  the  damage  in  a  very  short  time,  usually  within 
twenty-four  to  forty-eight  hours.  The  infected  parts  in 
both  rots  are  very  soft  and  water-soaked.  In  both,  the 
water  may  leak  out  through  some  break  in  the  epidermis, 
the  tissue  drying  in  proportion  as  the  water  is  lost. 

3.  Like  soft  rot,  ring  rot,  under  storage  conditions, 
does  not  send  out  sporophores  unless  a  break  occurs  on 
the  epidermis  and  this  usually  happens  through  the 
weight  and  pressure  of  the  surrounding  roots.  In  this 
case  the  sporophores  are  short,  very  numerous,  closely 
packed,  and  borne  at  the  break  in  the  epidermis  (Figs. 
9,  c;  II,  a). 

4.  As  in  soft  rot,  when  roots  freshly  infected  with 
ring  rot  are  placed  in  a  moist  chamber,  the  fungus  R. 
nigricans  grows  out  at  the  area  of  the  ring  within 
twenty- four  hours  (Fig.  11,  a). 

5.  In  plating  out  tissue  from  sweet  potatoes  freshly 
infected  with  ring  rot,  one  obtains  a  pure  culture  of  the 
Rhizopus  fungus  within  twelve  to  sixteen  hours. 

6.  Within  a  week  to  ten  days  after  infection,  the 
diseased  tissue  of  ring  rot,  just  as  in  soft  rot,  is  odorless, 
but  is  soon  followed  by  fermentation.  At  this  stage  the 
causative  organism  begins  to  die. 

7.  Ring-rotted  sweet  potatoes,  like  soft-rotted  ones, 
after  reaching  an  age  of  ten  days  to  three  weeks,  upon 
being  placed  in  a  moist  chamber,  fail  to  develop  any 
Rhizopus  growth  from  the  infected  area.  Platings 
made  from  these  roots  fail  to  produce  any  Rhizopus 
growth,  but  on  the  contrary  produce  fungi  like  Oospora 
lactis,  Oosporoideae  lactis  and  bacteria  (Fig.  9,  f). 
Crushed  mounts  of  the  tissue  from  old  ringed  areas 
under  the  microscope  reveal  the  presence  of  the  Rhizo- 
pus fungus,  the  filaments,  however,  being  empty  or  the 


Specific  Diseases  135 

protoplasm  browned  and  broken  up  into  small  granules, 
indicating  the  absence  of  life  in  these  hypae. 

Control  of  Soft  and  Ring  Rot.  The  factors  which 
are  favorable  for  the  development  of  these  diseases  in 
the  field,  the  hot-bed  and  in  storage  have  already  been 
pointed  out.  Much  can  be  done  to  reduce  the  losses  to 
a  minimum.  This  is  especially  true  under  storage  con- 
ditions. What  is  primarily  essential  is  an  abundance 
of  ventilation  wherever  the  weather  is  favorable.  This 
is  accomplished  only  in  properly  built  houses.  (For  fur- 
ther discussion  see  p.  216. )  In  the  seed  bed  soft  rot  and 
ring  rot  are  controlled  by  dipping  the  seed  in  corrosive 
sublimate  solution,  see  p.  24. 

Other  Pa/rasitic  Rhizopus.  The  work  of  Harter  (50) 
has  shown  that  there  are  species  of  Rhizopus  other  than 
R.  nigricans  which  may  produce  decay  on  the  sweet 
potato.  These  are  as  follows :  Rhizopus  tritici,  R.  no- 
dosus,  R.  niaydis,  R.  refiexus,  R.  artocarpi,  R.  delemar, 
R.  arrhisus,  and  R.  oryzae.  Rhizopus  chinensis  and  R. 
microsporus  do  not  seem  to  be  parasitic  on  the  sweet 
potato. 

MucoR  Rot 

Caused  by  Mucor  racemosus  Fes. 

Symptoms.  Mucor  rot  is  strictly  a  storage  disease, 
but  of  less  economic  importance  than  soft  rot.  The  tis- 
sue of  infected  potatoes  becomes  clayish-white  in  spots, 
somewhat  wet  but  spongy  to  firm  (Fig.  19,  f).  When 
a  rotted  potato  is  broken  open  it  pulls  out  in  a  fibrous, 
stringy  manner,  and  has  a  distinct  starchy  odor.  Mucor 
rot  was  worked  out  by  Harter  and  his  associates  (51), 
who  found  it  to  occur  only  under  low  temperature  con- 
ditions in  storage.  A  temperature  of  40  degrees  F.  and 
less  is  especially  favorable  for  infection. 


CHAPTER  X 
SPECIFIC  DISEASES  (Continued) 

GiBERELLA  ROT 

Caused  by  Giber ella  saubinettii  (D.  and  M.)  Sacc. 

GiBERELLA  Tot,  like  Mucor  rot,  is  of  little  economic 
importance.  It  is  only  found  on  sweet  potatoes  in 
storage  which  were  kept  at  a  low  temperature  of  about 
40  degrees  F.  Under  these  conditions,  Harter  and  his 
associates  (51)  were  able  to  obtain  infection.  Diseased 
sweet  potatoes  are  at  first  spongy  in  texture  and  brown 
in  color.  As  the  moisture  escapes,  the  tissue  becomes 
firm,  hard,  and  mummified.  The  brown  color  is  later 
replaced  by  a  pinkish-brown  tint. 

Dry  Rot 

Caused  by  Diaporthe  batatatis  (E.  and  H.)  Hart,  and 
Field 

Dry  rot  was  first  mentioned  by  Halsted  (27)  as  oc- 
curring in  New  Jersey,  the  cause  of  which  he  attributed 
to  an  undescribed  species  of  Phoma.  Twenty-two  years 
later,  Harter  and  Field  (43)  recognized  its  importance, 
and  succeeded  after  careful  investigations  in  proving 
that  dry  rot  was  caused  by  the  fungus,  Diaporthe  Ba- 
tatatis. The  disease  is  prevalent  in  New  Jersey,  Dela- 
ware, Virginia,  Mississippi,  Texas,  Alabama,  Indiana 
136 


Fig.  12.     Dry  Rot. 

a.  Surface  view  of  dry-rotted,  mummified  sweel  polalocs.  h.  Sweet  potato 
stem  to  show  the  pycnidia  of  tlic  dry-rot  orf^ani.siu.  c.  Photomicograph  of 
cross-section  through  a  pycnidium  of  the  dry-rot  (jrganism.  d.  Same  as  c 
but  longitudinal  section,  e.  The  .same  as  c  but  tangential  section  showing  the 
arrangement  of  the  pycnidia  in  the  stroma.  ^,  //,  and  k.  Stylospores.  /.  Tan- 
gential sections  of  .sweet  potato  showing  the  chambering  of  a  pycnidium  which 
contains  stylospores.  i.  Conidiophores  and  pycnidia.  j.  Clul)  shaped  stylo- 
spores  found  in  connection  with  an  ascospore  strain.  /.  and  m.  Germination 
of  pycniospores.  n.  Tangential  section  through  a  pcrithecium  showing 
asci  and  ascospores.  o.  Perithecia  borne  in  stroma.  />.  Asci  and  ascosporcs. 
q.  Germination    of    ascosporcs.     {h,  d  and  o  after  Harter  and  Field.) 


Specific  Diseases  137 

and  North  Carolina.  It  is  probable  that  dry  rot  Is  of 
much  wider  occurrence.  However,  it  may  be  easily 
overlooked  as  it  is  often  obscured  by  stem  rot  and  black 
rot. 

A  Field  Trouble.  It  is  not  always  easy  to  detect  the 
disease  in  the  field.  The  causal  fungus  works  very 
slowly,  and  the  pycnidia  are  formed  orily  when  the  plant 
is  in  a  dying  condition.  However,  languid  plants  may 
be  suspected  of  being  affected  with  the  dry  rot.  The 
fungus  may  attack  any  part  of  the  vines,  causing  it  to 
turn  brown,  shrunken,  and  in  time  become  covered 
with  the  characteristic  pycnidia  (Fig.  12,  a  and  b). 

A  Seed  Bed  Disease.  The  sprouts  from  diseased 
sweet  potatoes  seem  at  first  healthy.  Later,  however, 
the  vines  start  to  die  at  the  nodes  and  the  disease  fre- 
quently works  down  to  the  base  of  the  sprout.  The 
disease  is  found  on  old  abandoned  hot-beds,  late  in  the 
season.  It  is  very  likely  that  dry  rot  is  carried  with  the 
seed  sweet  potatoes,  which  communicate  it  later  to  the 
sprouts.  Pycnidia  of  the  causal  organism  form  in 
abundance  as  soon  as  the  vines  die.  They  do  not  seem 
to  develop  on  languid  or  partly  living  tissue. 

A  Storage  Disease.  In  storage,  the  dry  rot  makes  its 
appearance  about  six  to  eight  weeks  after  digging. 
Diseased  potatoes  are  dried  and  shriveled,  later  becom- 
ing hard,  mummified,  and  covered  with  numerous 
pycnidia  (Fig.  12,  a). 

The  Organism.  Diaporthe  batatatis  has  two  spore 
stages,  the  pycnidia  and  the  asci.  On  the  roots,  the 
pycnidia  are  at  first  buried  (Fig.  12,  c)  later  breaking 
through  the  epidermis  by  a  single  opening  (ostiole). 
The  pycnidia  are  irregularly  chambered  (Fig.  12,  d,  e, 
f,  o),  and  vary  in  size,  often  uniting  and  forming  a 
continuous  chamber.    Frequently  the  opening  (ostiole) 


138  The  Sweet  Potato 

is  as  long  as  the  pycnidium  Itself  (Fig.  12,  d)",  which  Is 
carbonaceous  at  the  outside  wall,  but  hyaline  in  its  inner 
part.  The  pycniospores  are  oblong  to  fusoid,  hyaline, 
usually  with  two  or  three  oil  droplets,  borne  on  long 
hyaline  basidia  (Fig.  12,  h  to  m).  In  the  pycnidia  Is 
also  found  another  type  of  spore  known  as  stylospores. 
These  are  filiform,  curved,  and  hook-shaped  bodies, 
which,  as  far  as  is  known,  no  one  has  as  yet  succeeded 
in  germinating  (Fig.  12,  k). 

The  ascogenous  or  winter  stage  was  not  found  on 
dead  sweet  potatoes  or  sweet  potato  material.  Harter 
and  Field  (43)  found  it  on  artificial  media.  The  peri- 
thecia  are  formed  in  a  stroma  (Fig.  12,  n),  which  Is 
ashy  gray  within,  black  outside,  and  possesses  subcylin- 
drical  beaks.  The  atroma  contains  from  9  to  25  perl- 
thecia,  and  the  latter  are  subglobose  (Fig.  12,  o).  The 
asci  are  clavate  to  cylindrical,  and  8-spored  (Fig.  12,  p). 
The  spores  are  arranged  in  one  or  two  rows  in  the  ascus, 
and  are  capable  of  germinating  in  three  to  five  hours. 

Control.  The  most  favorable  condition  for  dry  rot 
in  storage  is  a  relative  humidity  of  80  per  cent,  accom- 
panied by  high  temperatures.  As  far  as  possible  the 
relative  humidity  should  be  maintained  at  about  65  to 
70  per  cent.  This  may  be  accomplished  by  carefully 
regulating  the  temperature  and  the  ventilation. 

In  the  hot-bed,  infected  potatoes  should  never  be 
bedded,  but  should  be  boiled  and  fed  to  stock.  The 
sound  potatoes,  before  planting,  should  be  disinfected 
with  corrosive  sublimate  solution  (see  p.  24).  The 
soil  of  the  hot-bed  should  be  changed  every  year.  By 
carefully  selecting  healthy  seed  sweet  potatoes,  one  may 
keep  dry  rot  out  of  the  field. 


Specific  Diseases  139 

Phyllosticta  Leaf  Spot 

Caused  by  Phyllosticta  bataticola.  E.  and  M. 

Symptoms.  The  disease  appears  as  roundish  or 
angular  spots  which  are  more  prominent  on  the  upper 
side  of  the  foliage  (Fig  13,  a).  The  spots  are  separated 
from  the  healthy  tissue  by  a  dark  border.  Inside  this 
black  line  is  a  strip  of  brown  tissue  followed  by  a  circu- 
lar light  area  in  the  center.  The  pycnidia  of  the  causal 
organism  are  situated  in  the  center  of  the  spots;  they 
are  slightly  raised  and  domelike.  The  disease  is  found 
only  on  the  foliage,  and  is  not  known  to  attack  any  other 
host. 

Leaf  spot  occurs  everywhere  in  the  Southern  States. 
It  is  less  common  in  New  Jersey,  Delaware,  Maryland, 
Iowa,  Kansas  and  Illinois. 

Control.  The  disease  is  practically  of  no  economic 
importance,  as  it  attacks  the  foliage  at  the  end  of  the 
growing  season.  Plowing  the  old  vines  under  deep  is 
recommended. 

Foot  Rot  (Die  off) 

Caused  by  Plenodomus  destruens  Hart. 

Economic  Importance.  Foot  rot  is  an  old  disease,  but 
recently  has  been  worked  out  by  Harter  (34),  who  first 
found  it  in  Virginia.  There,  the  damage  from  this 
disease  runs  as  high  as  50  per  cent  of  the  total  crop. 
Foot  rot  has  also  been  found  in  Ohio,  Iowa,  Missouri, 
Kansas,  New  Jersey,  Maryland,  and  California. 

Symptoms.  Foot  rot  is  primarily  a  hot-bed  and  a 
field  disease.    It  is  usually  manifested  as  small  brown  to 


140  The  Sweet  Potato 

black  spots  on  the  stem  of  the  plant  near  the  soil  line. 
The  disease  at  first  progresses  very  slowly,  but  even- 
tually girdles  the  foot  of  the  vines  to  about  4  to  5  inches. 
At  this  stage  wilting  begins,  and  numerous  pycnidia 
form  on  the  dead  tissue.  Foot  rot  becomes  very  con- 
spicuous in  about  midsummer  or  later.  In  the  majority 
of  instances,  diseased  hills  produce  few  or  no  market- 
able potatoes. 

From  the  infected  stem,  the  disease  works  downward 
to  the  roots,  causing  a  brown  firm  rot  (Fig.  13,  b  to  c). 
During  digging  at  harvesting,  cuts  or  bruises  will  open 
the  way  to  infection,  and  the  disease  will  thus  be  carried 
from  the  field  to  the  storage  house. 

The  Organism.  The  pycnidia  (Fig.  13,  b)  according 
to  Harter  (34)  are  at  first  buried,  but  later  break 
through  the  epidermis,  appearing  as  scattered  black 
dots  (Fig.  13,  b).  They  are  irregular  in  form  and  vary 
much  in  size.  The  pycniospores  (Fig.  13,  k)  are  borne 
on  short  basidia,  and  are  oblong,  rounded  at  both  ends, 
hyaline,  one-celled,  and  slightly  curved.  Together  with 
the  spores  in  the  pycnidia  are  found  hyaline,  curved  or 
straight  bodies  (Fig.  13,  m),  the  exact  function  of 
which  is  as  yet  unknown. 

Control.  The  causal  organism  is  carried  over  winter 
on  the  dead  vines  in  the  field,  and  on  the  infected  seed 
sweet  potatoes.  It  is  doubtful  if  it  is  carried  over  much 
in  the  soil.  Dead  vines  from  infected  hills  should  be 
burned  as  soon  as  they  have  dried.  In  planting,  the  seed 
should  be  carefully  selected,  and  diseased  ones  discarded. 
Before  planting,  the  roots  should  be  disinfected  with 
corrosive  sublimate  (see  p.  24).  The  diseased  potatoes 
should  never  be  dumped  on  the  manure  pile,  and  should 
not  be  fed  raw  to  stock.  The  sand  in  the  hot-bed  should 
be  changed  every  year.    It  is  not  as  yet  definitely  known 


Fig.  13.    Foot  Rot. 

a.  Phyllosticta  leaf  spot.  h.  and  c.  Foot  rot  lesion.s  on  foot  enrl  of  sweet 
potato  vines,  d.  Longitudinal  section  showing  foot  rot  extended  from  vines 
to  root.  e.  Sweet  potato  hill,  the  foot  end  of  vines  being  girdled  by  fool  rot. 
/.  Section  of  pycnidium  on  the  root.  g.  Section  througli  a  pyciiidiuin  on  the 
stem.  //.  and  /.  Chlamydospore-like  buds  found  on  the  Iiost  and  in  culture 
media,  i.  Hyphae  from  pure  culture.  ^.  Pycniospores.  i.  and  /".  (MTiiiinating 
pycniosi)ores.  m.  Club-shaped  buds  frequently  found  in  i)ycnidia.  (c  after 
McClintock,  all  others  after  Harter.) 


Specific  Diseases  141 

how  long  the  disease  will  live  over  In  the  soil,  but  crop 
rotation  should  be  practiced  anyhow.  According  to 
Harter  and  his  associates  (51),  the  following  varieties 
were  inoculated  with  the  foot  rot  fungus  and  positive 
infection  obtained :  Yellow  Jersey,  Big  Stem  Jersey,  Red 
Bermuda,  Extra  Red  Carolina,  Southern  Queen,  Yellow 
Yam,  Pumpkin  Yam,  Vineless  Yam,  Dooley,  Triumph, 
Vineless  Pumpkin  Yam,  Nancy  Hall,  Florida,  General 
Grant,  Vineless  Yam,  White  Yam,  Red  Brazilian,  and 
Dahomey. 

Black  Rot  * 

Caused  by  Ceratostomella'fimbriata  (E.  and  H.)  Elliot 
Syn.  Sphaeronema  fimbriatum 

Economic  Importance.  Black  rot  is  an  important 
disease  of  the  sweet  potato.  It  occurs  in  the  hot-bed,  in 
the  field,  and  in  storage.  It  is  probably  found  wherever 
sweet  potatoes  are  grown.  Black  rot  was  reported  in 
New  Jersey,  Delaware,  Maryland,  Virginia,  Ohio,  Il- 
linois, Missouri,  Iowa,  Kansas,  Oklahoma,  Texas,  Ar- 
kansas, North  and  South  Carolinas,  Georgia  and  Ala- 
bama. 

Symptoms.  The  disease  is  first  introduced  in  the  hot- 
bed with  infected  potatoes.  On  the  young  sprouts,  in- 
fection begins  as  a  small  black  spot.  This  spot  gradu- 
ally involves  the  entire  shank,  which  dies  and  turns 
black,  whence  the  name,  black  shank  (Fig.  14,  b).  From 
the  hot-bed  the  disease  is  carried  to  the  field  with  in- 
fected sprouts.    There  the  symptoms  on  the  shanks  are 

*  Recently  Dr.  J.  A.  Elliot  has  shown  that  the  supposed  pycnidia 
and  pycniospores  of  Sphaeronema  fimbriatum  are  really  asci  ana 
ascospores,  hence  placing  it  in  the  genus  Ceratostomella.  (See  also 
Phytopath,  13:24,  1923.) 


142  The  Sweet  Potato 

the  same  as  on  the  sprouts  in  the  hot-bed.  Frequently 
also,  the  disease  attacks  the  vines  or  foliage,  in  which 
case  it  is  confined  to  intervals  of  a  few  nodes.  The 
infected  stems  or  foliage  (Fig.  14,  a)  turn  dark  and 
later  shrink  and  shrivel.  Infection  may  also  take  place 
under  ground  on  the  newly  forming  or  fully  matured 
roots.  From  the  field,  black  rot  is  carried  in  storage 
with  infected  potatoes.  On  the  latter  the  disease  ap- 
pears as  circular,  somewhat  sunken  black  spots  the  size 
of  a  silver  dollar  when  full  grown.  Black  rot  usually 
gains  entrance  through  the  young  rootlets,  or  through 
cracks,  wounds,  cuts,  or  bruises  in  the  mature  root,  in 
which  case  the  spots  lose  their  circular  outline.  Black 
rot  seldom  penetrates  the  entire  content  of  the  potato, 
but  only  advances  as  far  as  the  vascular  ring,  unless 
some  other  organism  opens  the  way  for  its  further 
progress.  In  the  field  and  in  the  hot-bed,  black  rot 
lives  over  from  year  to  year  in  the  soil.  In  storage,  the 
disease  spreads  by  contact  with  the  infected  potatoes. 
Overheating,  poor  ventilation,  and  excess  of  moisture 
furnish  ideal  storage  conditions  for  the  spread  of  black 
rot.  Under  moist  conditions,  the  causal  organism  pro- 
duces an  abundance  of  pycnidia  which  break  through 
the  epidermis  of  the  potatoes.  So  long  as  the  house  is 
kept  dry,  and  the  temperature  at  a  minimum  of  safety, 
the  disease  will  spread  very  little  in  storage. 

Black  Rot  Fungus  Is  Active  on  Several  Hosts.  The 
wild  morning  glory  {Ipomoea  purpurea)  (Fig.  14,  f) 
and  the  wild  sweet  potato  {Ipomoea  pandurata)  are 
probably  under  virgin  conditions  of  soil  the  most  active' 
hosts  in  carrying  the  fungus.  Thu?  it  seems  probable 
that  areas  which  have  never  grown  sweet  potatoes  are 
infected  with  black  rot  because  of  these  hosts.  It  would 
be  difficult  to  find  so-called  "virgin  land"  that  is  entirely 


Fic;.  14.     Black  Rot. 

a.  Black  rot  on  leaf.  b.  Black  shank  slaj,'c  on  sprout,  c.  Cros.s-section 
thronj^'h  black  rot  spfit  to  show  asci  of  black  rot  organism,  d.  Black  rot 
on  mature  root.  e.  Cross-section  through  black  rot  spot  on  root.  /.  Morning 
Glory  seedlings;  to  the  right,  two  healthy  plants,  to  the  left,  six  diseased 
with  black  rot.  g.  Endospore  formation,  h.  Cross-section  showing  chlamy- 
dosporcs  in  cells  of  potato  roots,  i.  Mycelium  breaking  up  into  spores. 
j.  Same  as  i,  also  showing  chalmydospores.  k.  Germination  of  conidia.  /. 
Ascus.     (d  and  /  after  Ilarter.) 


Specific  Diseases  I43 

free  from  the  disease,  for  so  many  agencies  are  at  work 
to  assist  in  the  broadcast  dissemination  of  the  causal  or- 
ganism. 

Susceptible  Varieties.  According  to  Harter  (36)  the 
following  varieties  are  susceptible  to  black  rot:  South- 
ern Queen,  White  Yam,  Big  Stem  Jersey,  Yellow  Jer- 
sey, Red  Bermuda,  Red  Brazilian,  Florida,  White  Gilke 
Hybrid,  Vineless  Pumpkin  Yam,  Pumpkin  Yam, 
Eclipse  Sugar  Yam,  Porto  Rico,  Triumph,  Yellow  Yam, 
Early  Carolina,  Miles  Yam,  Georgia,  Pierson,  Key 
West  Yam,  Nancy  Hall,  Red  Jersey.  This  list  includes 
most  of  the  widely  cultivated  varieties. 

The  organism.  Old  mycelium  is  darkish  gray,  with 
rather  close  septae,  and  usually  filled  with  oil  globules 
when  grown  on  media  rich  in  sugar.  The  young 
mycelium  is  hyaline  but  becomes  grayish  with  age.  The 
hyphae,  young  or  old,  are  capable  of  breaking  up  into 
-  as  many  cells  as  there  are  septae  and  each  cell  ger- 
minates like  a  spore  (Fig.  14,  i  and  j).  Another  stage 
of  spore  formation  corresponds  in  part  to  Thielavia; 
namely,  the  spores  are  borne  within  the  sheath  of  a  ter- 
minal cell,  and  these  are  pushed  out  from  within  (Fig. 
14,  g).  There  is  another  spore  stage  consisting  of 
olive-brown  conidia.  These  are  thick-walled,  and  are 
borne  singly,  by  twos,  or  in  chains.  These  brown  con- 
idia apparently  ser\^e  as  resting  spores,  since  it  takes 
them  a  much  longer  time  to  germinate.  This  type  of 
spore  is  often  found  in  the  interior  of  the  affected 
tissue,  in  the  cells  immediately  below  the  epidermis 
(Fig.  14,  j  and  h).  A  last  stage  is  that  of  asco- 
spores,  which  are  borne  in  long-necked  asci  (Fig. 
14,  c  and  1).  The  spores  are  globular,  minute,  oozing 
out  in  a  gelatinous  mass,  and  sticking  at  the  open  end 
of  the  long  neck  of  the  ascus.     Any  of  these  spores 


144  The  Sweet  Potato 

germinate  in  water  or  in  any  nutritive  fluid.  No  spore 
stages  other  than  those  above  mentioned  have  been  ob- 
served, in  pure  culture  or  on  the  host,  to  be  connected 
w^ith  Ceratostomella  fimbriata. 

Bitterness  of  Black  Rot.  When  roots  are  infected 
with  black  rot,  the  edible  qualities  are  poor  because  of 
the  bitter  taste.  This  becomes  more  evident  the  longer 
the  roots  are  kept  in  storage.  Although  the  black  rot 
spot  is  only  superficial,  the  bitter  taste  in  cooking  is 
imparted  to  the  entire  root,  showing  that  the  bitter  sub- 
stance of  black  rot  is  apparently  soluble  and  easily  dif- 
fused into  adjacent  tissue.  Because  of  this  fact,  every 
thing  possible  should  be  done  not  to  sell  black-rotted 
potatoes,  as  to  do  so  has  a  bad  effect  on  the  market,  and 
may  be  the  means  of  spreading  the  disease  to  new  terri- 
tories. There  seems  no  doubt  but  that  there  would  be 
a  greater  demand  for  sweet  potatoes  in  the  cities  if 
fewer  bad  ones  were  being  sold.  The  abused,  unsus- 
pecting consumer  has  a  way  of  retaliating  in  refusing 
to  buy  more. 

Control.  No  diseased  potatoes  should  be  bedded  in  the 
hot-bed.  They  should  be  carefully  selected  for  freedom 
from  disease  and  disinfected  in  corrosive  sublimate  be- 
fore planting  (see  p.  24).  Many  growers  insist  on  bed- 
ding black-rotted  potatoes  and  at  the  same  time  treating 
them  with  corrosive  sublimate.  This  treatment  will  posi- 
tively be  useless  if  it  is  done  on  black-rotted  potatoes. 
The  treatment  does  not  and  can  not  penetrate  the  inside 
of  the  potato  to  reach  the  fungus  in  the  tissue. 

Only  sprouts  from  healthy  hot-beds  should  be  planted 
out  in  the  field.  Badly  infected  fields  should  be  given  a 
rest  from  sweet  potatoes  for  several  years.  All  weeds 
belonging  to  the  Morning  Glory  family  should  be  de- 
stroyed.    Treating  the  soil  with    fertilizers,    gypsum, 


Fig.  15.     Java  Black  Rot. 

a.  and  d.  Cross-section  through  infected  root  showing  pycnidi 
b.  Surface  view  of  spot.  c.  Longitudinal  section  througli  /;.  c. 
of  Dip/odia  tubericola.  f.  Above  and  below,  formation  of 
g.  Mature  pycnidia.     (g  after  Harter.) 


I  on  the  host. 
Plate  culture 
p\-cniospores. 


specific  Diseases  145 

lime,   or  sulphur  will  have  little  effect  in  controling 
black  rot. 


Java  Black  Rot 

Caused  by  Diplodia  tubericola  (E.  and  E.)  Taub. 

Economic  Importance.  Java  black  rot,  so  called  be- 
cause it  was  first  found  in  Java,  and  is  believed  to  have 
been  introduced  from  that  country  to  the  United  States. 
The  disease  seems  to  be  a  storage  trouble  only,  and 
causes  some  loss.  It  was  studied  by  the  author  (95)  in 
Delaware.  The  disease  is  apparently  more  common  in 
the  Southern  States.  It  is  also  found  in  Cuba,  Isle  of 
Pines,  Philippine  Islands,  Japan,  Porto  Rico,  and 
throughout  South  America. 

Besides  the  sweet  potato,  Java  rot  can  also  attack  the 
dasheen  (Colocasia  esculenta).  Meier  (67)  found  that 
the  stem  rot  of  watermelon  was  caused  by  the  same  or- 
ganism as  that  of  Java  rot  from  sweet  potatoes. 

Symptoms.  Sweet  potatoes  affected  by  this  fungus 
show  dark  shriveled  patches,  over  which  are  scattered 
numerous  pvcnidia.  These  emit  either  mature  one-sep- 
tate dark  spores  heaped  together,  or  white  strings  which 
are  made  up  of  hyaline  Macrophoma  spores,  or  both. 
When  longitudinal  sections  are  made  through  different 
stages  of  affected  roots,  it  will  be  found  that  the  fungu? 
attacks  the  interior  tissue,  beginning  at  a  point  and 
gradually  invading  the  whole  of  the  interior  of  the  root 
(see  Fig.  15,  b  and  c).  The  infected  tissue  is  jet  black, 
somewhat  resembling  charcoal  rot.  Diseased  roots  dry, 
shrivel,  and  become  brittle. 

The  Organism.  Diplodia  tubericola,  grows  luxuria- 
antly  (Fig.  15,  e)  on  numerous  media.    The  organism 


146  The  Sweet  Potato 

produces  three  types  of  pycniospores  in  culture  as  on  the 
host.  These  are:  i  Hyaline,  one-celled.  2.  Dark  one- 
celled  spores.  3.  Dark  one-septate  spores  (Figs.  15,  f 
and  g) .  In  the  old  mummied  potatoes,  dark  two-celled 
spores  are  common.  The  pycnidia  (Fig.  15,  a  and  d) 
of  Diplodia  tubericola  on  sweet  potatoes  are  formed  im- 
mediately under  the  epidermis,  and  upon  maturity 
break  through.  Often  they  are  completely  buried,  in 
which  case  the  spores  escape  only  after  the  maceration 
or  disintegration  of  the  host.  Infection  seems  to  be 
favored  by  high  temperature  and  moisture  in  the  storage 
house.  The  rot  works  slowly,  requiring  four  to  eight 
weeks  to  completely  destroy  the  infected  potatoes. 

Control.  Since  Java  rot  seems  to  be  a  storage  disease 
only,  it  should  require  but  little  trouble  to  be  kept  in 
check.  Infected  material  should  be  destroyed  by  fire. 
The  storage  house  should  be  carefully  cleaned  and  dis- 
infected immediately  after  the  storage  season  (see 
p.  222). 


CHAPTER  XI 

SPECIFIC  DISEASES  (Continued) 

Septoria  Leaf  Spot 

Caused  by  Septoria  bataticola  Taub. 

Economic  Importance.  Septoria  leaf  spot  is  a  field 
disease  only.  It  usually  occurs  when  the  vines  are  full 
grown ;  hence  it  really  causes  little  damage.  It  is  prev- 
alent in  New  Jersey,  Delaware,  Maryland,  Virginia, 
Iowa  and  in  other  states  where  sweet  potatoes  are 
grown. 

Symptoms.  This  disease  is  characterized  by  minute 
white  spots,  ranging  from  one-eighth  to  one-third  inch 
in  diameter  (Fig.  i6,  a).  These  are  chalky  white,  bor- 
dered by  a  brown  area,  and  upon  close  observation  are 
found  to  bear  a  few  minute  pycnidia. 

The  Organism.  The  fungus  grows  well  (Fig.  i6,  b) 
on  moist  media.  The  pycnidia  on  the  host  vary  from 
one  in  the  center  to  a  few  scattered  ones  in  spots,  mostly 
circular,  chalky  white  bordered  by  a  brown  area,  and 
covering  the  leaf  sparsely  or  thickly.  The  pycnidia  are 
imbedded  under  the  epidermis  with  open  mouths  pro- 
truding, or  free,  readily  falling  out;  the  spores  are 
hyaline,  vermiform,  curved  to  straight. 

Control.  The  disease  is  not  serious  enough  to  war- 
rant methods  of  control. 

147 


148  The  Sweet  Potato 

Trichoderma  Rot 

Caused  by  Trichoderma  Koningi  Oud.,  or  Trichoderma 
lignorum  (Tode)  Harz. 

Economic  Importance.  Trichoderma  rot  is  a  storage 
rot  of  minor  importance.  It  has  been  found  by  Cook 
and  Taubenhaus  (13)  in  Delaware  on  sweet  potatoes 
infected  with  ring  rot.  Trichoderma  has  since  fre- 
quently been  isolated  from  rotted  potatoes  in  Texas. 
It  probably  may  be  found  in  other  states. 

Symptoms.  The  symptoms  of  the  disease  may  be 
given  as  follows:  In  their  earliest  stages  the  spots  are 
circular  and  of  a  light  brown  color  with  a  tendency  to 
wrinkle  (Fig.  17,  c  to  f ).  The  flesh  is  hard  and  water- 
soaked,  brown  in  color,  with  a  black  zone  at  point  of 
contact  between  the  healthy  and  diseased  tissue.  The 
spot  enlarges  in  all  directions  and  eventually  destroys 
the  entire  root.  When  the  decay  is  well  advanced,  a 
very  luxuriant  white  mycelial  growth  is  formed  on  the 
surface.  Spores  are  produced  very  sparingly  on  this 
growth  when  in  contact  with  the  decayed  tissue,  but 
very  abundantly  on  that  part  of  the  mycelium  which  has 
spread  over  the  healthy  surface.  The  symptoms  pro- 
duced by  T.  lignorum  are  very  similar  to  those  of  T. 
koningi,  except  that  a  deeper  brown  zone  separates  the 
diseased  from  the  healthy  tissues. 

The  Organism.  Trichoderma  lignorum  is  common 
and  widely  distributed  on  decaying  wood  and  various 
other  substances.  Trichoderma  koningi  was  originally 
isolated  from  the  soil  by  Oudemans  {/'6)  and  is  still 
looked  upon  as  a  soil  organism.  The  spores  of  T. 
lignorum  are  spherical  while  the  spores  of  T.  Koningi 
are  elliptical.    In  germinating  the  spores  of  T.  Koningi 


specific  Diseases  149 

form  one  to  two  germ  tubes,  while  the  spores  of  T. 
lignorum  in  germinating  send  out  two  or  three  germ 
tubes.  The  mycelium  of  T.  koningi  is  distinguished  by- 
its  great  abundance  of  chlamydospores  while  the  T. 
lignorum  very  rarely  produces  chlamydospores  (Fig. 
17,  i,  j,  k).  In  very  old  cultures  of  T.  koningi  the 
chlamydospores  are  frequently  free  and  in  a  state  of 
germination.  What  appear  to  be  haustoria  were  seen  in 
tissue  affected  with  T.  koningi.  The  conidophores  of 
the  two  organisms  do  not  show  distinguishing  char- 
acters (Fig.  17,  k).  When  grown  on  different  syn- 
thetic media  the  two  organisms  show  different  growth- 
characteristics  (Fig.  17,  a  and  b). 

Control.  The  disease  is  undoubtedly  brought  from 
the  field  to  the  storage  house  with  bruised  potatoes. 
Care  in  that  direction  will  be  very  helpful.  All  other 
precautions  necessary  to  control  soft  and  ring  rot,  will 
also  keep  the  Trichoderma  rot  in  check. 


BoTRYTis  Rot 
Caused  by  Botrytis  cinerea  Pers. 

Economic  Importance.  Botrytis  rot  is  of  little  eco- 
nomic importance.  It  may  generally  be  found  in  stor- 
age houses  where  the  temperature  is  rather  low.  Botrytis 
rot  has  been  reported  but  once  by  Harter  (51),  and  the 
extent  of  its  distribution  as  a  sweet  potato  disease  is 
not  known. 

Symptoms.  The  decay  produced  is  of  a  grayish,  soft, 
watery  nature  (Fig.  19,  n).  Infected  sweet  potatoes 
have  a  starchy  odor,  and  when  broken,  the  tissue  pulls 
out  in  strings.    No  methods  of  control  are  known. 


150  The  Sweet  Potato 

Soil  Stain  or  Scurf 
Caused  by  Monilochaetes  infuscans  E.  and  H. 

Economic  Importance.  Soil  stain  is  not  a  disease  to 
be  feared  in  the  sense  that  it  may  produce  a  direct  rot 
in  the  mature  roots ;  nevertheless,  it  is  economically  im- 
portant. Growers  whose  lands  are  badly  infected  assert 
that  stained  roots  keep  better  in  storage.  Others  find 
consolation  in  saying  there  is  no  such  thing  as  stain,  the 
dark  color  of  the  skin  being  merely  a  varietal  character- 
istic. The  fact  remains,  however,  that  many  eastern 
markets  discriminate  against  stained  roots.  In  years  of 
overproduction  the  New  York  market  refuses  stained 
roots.  The  Western  buyers,  on  the  contrary,  are  lax 
on  this  point;  otherwise,  many  growers  in  the  United 
States  would  be  forced  to  cease  producing  sweet  pota- 
toes for  want  of  a  market.  Soil  stain  is  prevalent  in 
the  following  states :  New  Jersey,  Delaware,  Maryland, 
Virginia,  North  Carolina,  Ohio,  Illinois,  Iowa,  Kansas, 
Texas  and,  in  fact,  wherever  sweet  potatoes  are  grown. 
Soil  stain  is  more  prevalent  in  the  heavy  black  soils,  and 
in  soils  which  were  heavily  manured,  though  it  occurs 
to  some  extent  in  the  sandy  and  sandy  loam  soils. 

Symptoms.  Soil  stain  is  primarily  a  field  trouble 
where  it  is  introduced  from  the  hot-bed  with  sprouts 
from  infected  seed  sweet  potatoes.  It  is  also  spread  to 
some  extent  in  the  storage  house  where  it  is  first  brought 
in  with  infected  potatoes  from  the  field.  Soil  stain  is 
characterized  at  first  by  small,  circular,  deep-clay-col- 
ored spots  on  the  surface  of  the  sweet  potato  root. 
These  spots  occur  singly,  but  usually  there  are  several 
in  a  given  area.  When  very  numerous,  the  spots 
coalesce,  forming  a  large  blotch,  which  sometimes  takes 


Specific  Diseases  151 

the  form  of  a  band  or  may  cover  the  entire  root  (Fig. 
16,  c  and  d).  Soil  stain  is  particularly  conspicuous  on 
the  white-skinned  varieties  such  as  the  Southern  Queen. 
Here  the  color  of  the  spots  is  that  of  a  deep  black  clay 
loam.  On  the  darker  skinned  varieties,  the  color  of  the 
spots  is  not  so  conspicuous.  Soil  stain  is  a  disease  of 
the  underground  parts  of  the  plant.  The  vines  and 
foliage  are  never  attacked  as  long  as  they  remain  free 
from  the  soil.  However,  when  these  are  covered,  the 
petioles  as  well  as  the  stems  become  infected.  The 
disease  penetrates  the  host  to  the  depth  of  the  epidermis 
and  it  may  be  readily  rubbed  off  by  the  finger  nail. 

After  several  months  of  storage,  badly  affected  roots 
become  a  deep  brown,  which  greatly  contrasts  with  non- 
infected  sweet  potatoes.  Occasionally,  badly  stained 
roots  seem  to  be  subject  to  more  rapid  drying  and 
shrinking.  This,  however,  is  not  often  the  rule.  Usually 
soil  stain  is  very  prevalent  in  overheated  storage  houses. 
It  may  be,  therefore,  that  the  rapid  shrinkage  is  due  to 
the  overheating  and  not  to  the  effect  of  the  disease  itself. 

The  Organism.  Monilochaetes  infuscans  was  studied 
by  Halsted  {2y),  Harter  (38)  and  by  the  author  (99). 
The  surface  growth  of  a  colony  resembles  that  of 
species  of  Alternaria  and  some  species  of  Cladosporium, 
but  differs  from  these  by  its  restricted  slow  growth 
(Fig.  16,  g).  The  surface  of  the  colony  of  M.  infuscans 
has  an  ashen  color,  which  is  also  the  general  appearance 
of  the  fruiting.  The  fungus  grows  better  on  vegetable 
plugs  and  is  at  its  best  on  steamed  onion  and  celery 
stalks.  The  aerial  mycelium  is  branched,  separate,  and 
hyaline  when  young;  with  age  it -turns  gray,  then  black, 
and  becomes  filled  with  oil  globules.  The  submerged 
hyphae  are  made  up  of  smaller  cells  which  in  old  cul- 
tures swell  and  take  on  the  appearance  of  chlamydo- 


152  The  Sweet  Potato 

spores.  The  conidiophores  are  distinct  from  the  my- 
celium (Fig.  i6,  f )  and  do  not  seem  to  arise  in  clusters, 
but  are  formed  singly.  They  are  erect,  unbranched, 
and  made  of  closely  septate  dark-celled  mycelium,  the 
base  of  which  rests  on  one  or  two  smaller  ones  (Fig. 
i6,  e).  Generally  the  measurements  of  the  conidio- 
phores vary  with  the  medium  used.  The  host,  too, 
seems  to  have  a  determining  influence. 

The  spores  are  borne  in  distinct  chains.  In  a  pure 
culture,  the  chains  break  up  very  readily  when  moist- 
ened and  pressed  down  with  a  cover  glass.  The  spore 
chains  break  immediately  when  moistened  with  alcohol, 
oil,  or  any  other  liquid  (Fig.  i6,  f).  The  chains  of 
spores  do  not  appear  to  be  held  together  with  any  kind 
of  mucilage.  At  first,  the  protoplasm  of  the  tip  of  the 
conidiophore  is  seen  to  round  up;  then  a  minute  bud 
pushes  out  and  increases  in  size  until  a  mature  spore  is 
developed,  which  is  left  standing  at  the  tip  of  the  conidio- 
phore (Fig.  1 6,  f).  All  the  succeeding  newly  formed 
conidia  are  borne  at  the  tip  of  the  conidiophore,  so  that 
the  oldest  conidium  stands  at  the  farthest  end  of  the 
chain  (Fig.  i6,  f).  These  chains  are  made  up  of  ten  to 
twenty-eight  conidia.  A  distinct  characteristic  of  the 
latter  is  that  they  are  always  guttulate,  irrespective  of 
the  medium  used.  In  some  cases  the  conidia  in  pure  cul- 
ture appear  to  be  massed  in  "pockets"  around  the  tip  of 
the  conidiophore,  as  in  species  of  Gloeosporium  or 
Fusarium.  However,  a  close  examination  will  show 
that  this  is  not  a  definite  characteristic  of  the  fungus, 
since  the  least  disturbance  will  cause  the  chains  of 
conidia  to  break  up.  In  so  doing  they  invariably  cluster 
around  the  conidiophore,  grouping  themselves  in  various 
ways.  This  is  observed  only  when  the  fruitings  of  the 
fungus  are  seen  in  a  dry  state.    However,  when  placed 


Fig.  i6.    Soil  Stain. 

a.  Septoria  leaf  spot.  b.  and  g.  Pure  cultures  of  Moni'ochaetes  infuscans. 
c.  and  d.  Soil  stain  spots  on  roots,  e.  Cross-section  tlirou^di  sweet  potato  root 
to  show  the  K'rowth  of  llie  soil  stain  fungus  on  the  host.  /.  Stages  in  the  formation 
of  coniilia  of  M.  infnscniis. 


Specific  Diseases  153 

in  a  drop  of  water  or  in  any  other  liquid,  the  chains  of 
spores  break  up  and  scatter  irregularly  over  the  liquid. 
The  spores  (conidia)  are  one-celled,  hyaline,  with  a 
greenish  tinge,  but  never  dark  or  brown.  Sometimes  a 
tube  is  produced  at  the  tip  of  the  conidiophore  which 
later  bears  spores.  Broken-off  mycelial  cells  are  also 
capable  of  germinating.  The  spores  readily  germinate 
in  water  or  in  any  nutrient  medium. 

An  attempt  was  made  by  the  author  to  determine 
whether  M.  inftiscans  would  also  cause  a  rot  of  the  in- 
terior of  the  sweet  potato  root.  Inoculations  with  pure 
cultures  of  the  fungus  in  slits  made  with  a  sterilized  and 
cooled  scalpel  showed  the  organism  incapable  of  causing 
a  rot  of  the  root. 

Control.  Soil  stain  is  carried  directly  with  the  seed 
sweet  potatoes.  As  far  as  possible,  stained  potatoes 
should  not  be  used  for  bedding,  because  the  roots  may 
also  be  infected  with  black  rot,  and  yet  the  latter  will 
be  obscured  by  the  blackened  skin.  Potatoes  with  but 
few  and  scattered  stain  spots  may  be  bedded  in  the  hot- 
bed, provided  they  are  disinfected  with  corrosive  sub- 
limate (see  p.  24). 

In  the  field,  infected  soils  should  be  avoided  if  pos- 
sible and  should  receive  no  manure.  According  to  Har- 
ter  (38),  the  following  varieties  are  susceptible  to  soil 
stain:  Eclipse  Sugar  Yam,  General  Grant  Vineless, 
Florida,  Nancy  Hall,  Yellow  Yam,  Miles  Yam,  Red 
Brazilian,  Red  Bermuda,  Japan  Brown,  Dahomey,  Yel- 
low Strasburg,  Pierson,  Key  West  Yam,  Red  Gilke 
Hybrid,  Vineless  Pumpkin  Yam,  Pumpkin  Yam,  Porto 
Rico,  Triumph,  Vineless  Yam,  Southern  Queen,  Big 
Stem  Jersey,  Yellow  Jersey,  and  Early  Carolina  Creole. 
It  is  also  likely  that  soil  stain  occurs  on  other  varieties 
of  sweet  potatoes. 


154  The  Sweet  Potato 

In  storage,  proper  care  should  be  given  to  heating  and 
ventilation.  The  disease  is  always  worse  in  damp,  over- 
heated, and  poorly  ventilated  storage  houses. 


Alternaria  Rot 
Caused  by  Alternaria  sp. 

Among  the  many  organisms  which  produce  storage 
rots  at  low  temperatures  may  be  mentioned  a  species  of 
Alternaria.  It  produces  a  firm,  moist  rot  (Fig.  19,  o), 
the  tissue  turning  brown,  and  then  gradually  darkening, 
but  never  becoming  black.  The  infected  potato  breaks 
easily,  and  the  parts  separate  without  the  formation  of 
strands. 

Vine  Wilt,  or  Stem  Rot,  Blue  Stem 

Caused  by  Fusarium  hyperoxysporiim  Woll,  Fusarium 
hatatatis  Woll. 

Economic  Importance.  Stem  rot  in  some  states  is 
equally  as  important  as  black  rot  (see  p.  141)  or  even 
pox  (see  p.  107) •  The  losses  vary  from  2  to  90  per  cent. 
The  disease  is  prevalent  in  New  Jersey,  Delaware, 
Maryland,  Virginia,  Illinois,  Iowa,  Kansas,  Alabama, 
Arkansas,  Missouri,  North  Carolina,  Ohio,  Georgia, 
Oklahoma  and  Mississippi.  In  many  of  the  Southern 
States,  the  disease  is  usually  not  serious,  as  some  of  the 
Southern  varieties,  the  Nancy  Hall  excepted,  seem  to 
be  more  resistant.  The  disease  was  studied  by  Hal- 
sted  {27),  Stevens  (89),  Harter  {z^),  McClintock 
(64),  and  the  author  (97). 

Symptoms.  The  first  indication  of  vine  wilt  in  the 
field  is  a  slight  paleness  of  color.     The  leaves  become 


Trichoderma  Rot. 


Plate  cultures  of  Trichoderma     iniorum. 


I,    Plate  culture  of  T.  koniiii^i. 
f.  Sweet 


i''<-'i^-'''^':^f'''-'-'  ^'^'\,J''-u"'7,Zi      ,    Same  as?.     /.  Germinatini;  spores 
right,  7".  koningi';  to  left,  T.  Ungorum. 


Specific  Diseases  155 

dull  and  then  yellowed  between  the  veins  and  puckered. 
This  is  followed  by  a  wilting  of  the  vines  in  the  hill. 
Usually  the  tip  leaves  on  the  vines  are  the  first  to  show 
the  effects  of  the  wilt.  As  a  rule,  the  old  basal  leaves 
drop  off  if  the  vine  becomes  infected.  Frequently  but 
one  or  two  vines  in  the  same  hill  will  remain  alive  while 
all  the  others  will  die.  Usually,  however,  all  the  vines 
die  off  and,  soon  after,  new  shoots  start  out  from  the 
base  of  the  plant  (Fig.  i8,  b  and  c).  In  this  case  the 
vines  only  and  not  the  roots  are  killed.  Frequently  in- 
fected hills  straggle  along  and  even  produce  potatoes, 
but  these  are  usually  small  (Fig.  i8,  e)  and  are  often 
unintentionally  used  for  seed. 

The  Organisms.  The  causal  organisms  of  vine  wilt 
invade  the  vascular  bundles  of  the  vines  and  roots. 
When  the  tip  end  of  an  infected  potato  is  cut  with  a 
sharp  knife,  the  vascular  bundles  will  be  found  to  be 
brown  (Figs.  i8,  a,  d,  e  and  19,  a).  When  an  infected 
sweet  potato  vine  is  split  lengthwise,  the  inside  too  will 
be  brown  to  dark;  whereas  a  healthy  vine  will  have  a 
white  interior  (Fig.  18,  d). 

In  the  hot-bed,  vine  wilt  is  manifested  in  the  same 
way  as  in  the  field.  Diseased  plants  may  be  detected  by 
a  faint  purplish  tint  of  the  stem,  and  the  yellow  discol- 
oration of  the  leaves.  The  organisms,  Fusarium  hatatatis 
Woll.,  in  pure  culture  produce  conidia,  sporodochia, 
and  pionnotes ;  the  Conidia  (Fig.  19,  c  and  d)  are  mostly 
three-septate,  rarely  four-  or  five-septate.  The  chlamy- 
dospores  are  brown  and  thick.  The  blue  sclerotia  have 
a  blister-like  appearance.  Fusarium  hyperoxysporum 
Woll.  (Fig.  19,  a)  resembles  F.  oxysporum  but  differs 
from  it  by  having  perfect  pionnotes.  Both  jF.  hatatatis, 
and  F.  hyperoxysporum  (Fig.  19,  c  and  d)  were  orig- 
inally described  by  Wollenweber  (116). 


156  The  Sweet  Potato 

Control.  It  has  been  indicated  that  the  causal  organ- 
isms enter  the  roots  where  they  remain  in  the  jfibrovascu- 
lar  bundles.  Such  roots  when  harvested  and  put  in 
storage  do  not  rot.  Early  in  the  spring,  when  these  in- 
fected potatoes  are  bedded  in  the  hot-bed,  the  disease 
will  infect  the  sprouts  (Fig.  18,  a)  and  thence  will  be 
carried  to  the  field.  It  is,  therefore,  of  extreme  im- 
portance to  secure  only  healthy  seed  sweet  potatoes. 
When  one  is  in  doubt,  the  tip  end  of  the  potato  should 
be  cut  off  with  a  sharp  knife,  and  potatoes  with  dark 
brown  fibers  should  not  be  bedded.  These  may  be 
cooked  and  fed  to  stock.  Before  being  bedded,  the  po- 
tatoes should  be  disinfected  in  corrosive  sublimate  (see 
p.  24).  This  treatment  will  not  kill  the  vine  wilt  fungus 
within  the  potato,  but  will  destroy  any  spores  which 
may  adhere  on  the  surface. 

The  sand  in  the  hot-bed  should  also  be  changed  every 
year.  Fresh  sand  should  be  procured  from  that  part  of 
the  farm  which  never  grew  sweet  potatoes  before.  Each 
year,  the  wooden  frame  work  of  the  hot-bed  should  be 
disinfected  by  wetting  it  with  a  solution  of  one  pint  of 
formaldehyde  in  thirty  gallons  of  water,  or  with  a  solu- 
tion made  up  of  five  pounds  of  blue  stone  (copper  sul- 
phate) dissolved  in  fifty  gallons  of  water.  This  treat- 
ment should  be  given  twice  at  an  interval  of  twenty-four 
hours. 

The  application  of  lime,  gypsum  salt,  or  any  other 
fertilizer  to  the  soil  with  a  view  of  warding  off  vine  wilt 
will  be  of  no  value.  Where  vine  wilt  is  prevalent,  seed 
from  vine  cuttings  are  preferred.  The  cutting  should  of 
course  be  made  from  healthy  vines,  and  planted  on 
healthy  ground.  In  infected  regions,  crop  rotation 
should  be  practiced,  and  the  land  given  a  rest  from  sweet 
potatoes  for  at  least  three  or  four  years. 


0 


■■"^•^ 


/ 


Fig.  i8.     Fusarium  Wii.t. 

a.  Cross-section  through  infected  sweet  potato  PMit  showin.:;  liow  I'usariuni 
wilt  is  communicated  to  the  younj,'  sprout  throuk'li  the  f hro-vascular 
bundles  of  the  mother  root.  />.  Below,  sweet  potato  hill  killed  hy  Fu.sarium 
wilt;  above,  healthy  hill.  r.  Like  b,  l)ut  new  sjirouts  orii,'inatin«  from 
center  of  hill.  d.  f.onuitudinal  section  fur  compari.sim:  to  left.  <liseased 
stem;  to  riudit,  healthy  stem.  r.  Two  sweet  [lotato  hills  from  infected 
plants.    /.  Sweet  potato  hill  from  healthy  plant. 


Specific  Diseases  I57 

Harter  and  Field  (44)  have  shown  through  actual 
inoculation,  that  certain  Southern  varieties  possess  con- 
siderable resistance  to  wilt.  These  are  the  Dahomey, 
Red  Brazilian,  and  Yellow  Strasburg.  However,  the 
growing  of  these  varieties  other  than  in  the  Southern 
States  could  not  be  advocated.  A  variety  which  may  be 
prolific  in  one  region  may  be  a  very  poor  yielder  when 
introduced  in  a  new  locality.  The  Yellow  Jersey,  for 
instance,  produces  a  fine  potato  in  New  Jersey  or  Dela- 
ware, but  greatly  deteriorates  when  grown  in  the  South. 
Moreover,  the  market  requirements  are  to  be  considered. 
The  Northern  markets  which  prefer  a  dry,  mealy  sweet 
potato  will  not  readily  accept  the  yam  type  of  the 
South.  Hence,  methods  of  control  based  on  resistant 
varieties  offer  little  promise.  The  only  solution  is  the 
development  of  resistant  local  strains  by  selection.  This, 
however,  has  not  shown  much  promise  in  the  past. 

Surface  Rot 
Caused  by  Fusarium  oxysporum  Schl. 

Surface  rot  of  the  sweet  potato  is  generally  a  storage 
trouble.  It  appears  as  nearly  circular,  brownish, 
somewhat  sunken  spots  on  the  surface  of  the  stored 
roots.  Sweet  potatoes  thus  affected  shrink,  especially 
at  the  margin  of  the  spots.  In  severe  cases  the  entire 
root  dries  up,  becoming  unfit  for  eating  purposes. 

According  to  Harter  and  Weimer  (48)  infection 
takes  place  at  digging  time  during  wet  weather  or  early 
in  the  storage  period  under  low  temperature  conditions. 

Control.  As  far  as  possible  digging  should  be  done 
during  dry  weather.  Furthermore,  the  roots  should  not 
be  brought  in  wet  to  storage,   nor  the   storage  house 


158  The  Sweet  Potato 

permitted  to  cool  off  during  the  early  process  of  sweat- 
ing. 

Other  Fusarium  Rots 

It  has  been  shown  by  Harter  (51)  that  Fusarium  cul- 
morum  Woll.  and  F.  accuminatum  E.  and  E.,  may  pro- 
duce a  storage  rot  under  low  temperature  conditions.  The 
symptoms  are  a  slow  decay,  the  affected  tissue  becoming 
spongy  but  not  watery.  At  first  the  decayed  tissue  is  a 
faint  reddish-brown  which  later  turns  carmine-red,  or 
maroon.  As  the  potato  dries  out  and  becomes  mummi- 
fied, the  deep  color  is  replaced  by  a  beautiful  pink. 

The  following  Fusaria  isolated  from  sweet  potatoes 
do  not  seem  capable  of  inducing  any  rot  in  storage:  F. 
hatatatis  Woll. ;  F.  hyperoxysporum  Woll. ;  F.  radicicola 
Woll.;  F.  caudatum  Woll.;  F.  solani  (Mart.)  Sacc. ; 
F.  incarnafum  (Rob.)  Sacc;  F.  orthoceras  Appel  and 
Woll. ;  F.  orthoceras  var.  triseptatum  Woll. ;  F.  oxy- 
sporwm  Sch. ;  Nectria  ipomoeae  Hals. 


CHAPTER  XII 

SPECIFIC  DISEASES  (Continued) 

Epicocum  Rot 

Caused  by  Epicocum  sp. 

Epicocum  rot  cannot  be  considered  of  much  economic 
importance.  It  is  found  under  low  temperature  condi- 
tions in  the  storage  house.  The  rotting  is  slow,  the 
affected  tissue  is  firm,  at  first  slightly  yellowish,  then 
reddish-brown  (Fig.  19,  1). 

Charcoal  Rot 

Caused  by  Sclera  Hum  bataticola  Taub. 

Economic  Importance.  Charcoal  rot  is  a  storage  rot 
only,  distributed  throughout  the  United  States  and 
elsewhere.  It  has  been  collected  by  Harter  (51)  from 
specimens  of  sweet  potatoes  received  from  Japan  and 
other  foreign  countries.  The  same  disease  is  also 
known  to  attack  green  peppers. 

Symptoms.  Charcoal  rot  is  commonly  mistaken  for 
black  rot.  While  black  rot  produces  only  superficial 
spots  on  the  roots,  and  does  not  produce  a  rot  of  the 
entire  root,  charcoal  rot  is  a  disease  that  penetrates  the 
entire  root.  The  parasite  does  not  produce  surface 
spots,  but  turns  the  interior  tissue  into  a  black  charcoal 
mass  (Fig.  19,  g)  caused  by  the  formation  of  minute, 
black  sclerotia.  With  the  exception  of  drying  and 
159 


i6o  The  Sweet  Potato 

slight  shrinkage,  unless  the  skin  is  bruised,  showing  the 
blackened  contents,  there  are  no  external  symptoms  to 
distinguish  this  disease.  It  can  be  recognized  only  when 
the  roots  have  been  completely  invaded  and  broken  open. 

The  Organism.  Sclerotium  bataticola  was  thought 
by  Halsted  (27),  Burnette  (7),  Townsend  (107),  Wil- 
cox (114)  and  Duggar  (17)  to  be  a  stage  of  the  black 
rot  fungus,  Ceratostomella  fimbriata.  However,  work 
by  the  author  (95)  has  shown  that  Sclerotium  bataticola 
was  a  distinct  organism,  and  in  no  way  related  to 
Ceratostomella  fimbriata.  The  Sclerotia  are  jet  black, 
and  minute;  they  have  a  smooth  exterior,  made  up  of 
anastomised  black  hyphae;  the  interior  is  light  to  dark 
brown  in  color,  made  up  of  free,  thick-walled,  cortical, 
hyphal  cells ;  sclerotia  vary  much  in  shape,  being  spheri- 
cal, oval,  oblong,  elliptical,  curved,  or  even  forked ;  they 
also  vary  in  size  (Fig.  19,  i  to  k),  are  abundant  through- 
out the  entire  root  of  the  host,  and  are  parasitic  on  liv- 
ing roots  of  sweet  potato. 

Control.  Charcoal  rot  Is  prevalent  In  overheated  and 
poorly  ventilated  storage  houses.  The  method  which  will 
control  soft  rot  (see  p.  135)  may  also  control  charcoal 
rot. 

Cottony  Rot 

Caused  by  Sclerotium  rolfsii  Sacc. 

Economic  Importance.  Cottony  rot  is  a  trouble  that 
occurs  primarily  in  hot-beds,  where  it  often  destroys  ten 
to  forty  per  cent  of  the  sprouts.  It  is  met  with  fre- 
quently in  the  field  and  occasionally  in  storage.  Cottony 
rot  also  attacks  corms  of  Colocasia  esculenta,  of  Xan- 
thosoma  sagittifolium,  and  a  large  number  of  other 
hosts. 


Fig.  iq. 


Various  Diskas; 


a  Pure  culture-  uf  Pusarium  isolated  from  diseased  sweet  potato  root 
A.  YouuK  uafected  hill  showinK  bursting  of  the  mam  ^a^^l  ^me  and  r„o^ 
due  to  the  wUt  disease,  c.  Spores  of  Fusanum  balulaUs.  ';^^\^^f;^'y^ 
peroxvsporum.  d.  Cross-section  of  sweet  potato  root  shmMUK  xnlcLUonjX 
the  fibrS-vaseular  bundles.  /.  Mucor  rot.  ^'.  Charcoal  rot.  /.  ^  /r.  StaRes 
in  Sclerotia  formation  of  ScleroUum  bataUcola  I  ^^P'^-^^^V  '•„'..  "'^^^- 
lium  rot.     n.   Bolrytis  rot.     o.  Alternaria  rot.     (/.  /.  to  o.  after  Harter.) 


Specific  Diseases  i6i 

Sympioms.  In  the  early  stage  of  infection,  the  foot 
of  the  sprout  becomes  soft,  watersoaked,  and  covered 
at  the  exterior  by  a  cottony  white  growth  of  fungus 
mycelium.  Later  numerous  sclerotia  the  size  of  a  mus- 
tard seed  are  formed  all  over  the  dead  sprouts.  From 
the  plant,  the  fungus  works  down  into  the  mother  potato 
causing  it  to  rot  slowly.  In  storage,  cottony  rot  is  not 
common,  but  occasionally  found  there.  Affected  pota- 
toes become  punky  and  dry.  If  a  freshly  infected  potato 
is  cut  open  and  placed  in  a  moist  chamber,  the  mycelium 
of  the  causal  organism  will  grow  out  profusely  on  the 
walls  of  the  glass. 

The  Organism.  Sclera  Hum  rolfsii,  as  far  as  we 
know,  is  a  sterile  fungus.  It  reproduces  by  means  of 
sterile  mycelium  and  sclerotia,  the  latter  of  which  may 
live  over  in  the  soil  from  year  to  year.  As  soon  as  the 
disease  makes  its  appearance  in  the  hot-bed,  the  affected 
area — plants  and  soil — should  be  carefully  lifted  out 
with  a  spade.  The  water  should  be  withheld  and  the 
hot-bed  given  plenty  of  ventilation  and  sunlight.  Treat- 
ing the  seed  sweet  potatoes  with  corrosive  sublimate 
(see  p.  24)  before  bedding  will  also  be  helpful. 


Texas  Root  Rot 
Caused  by  Osonium  omnivorum  (Pam.)  Shear 

Economic  Importance.  Texas  root  rot  is  primarily 
a  field  trouble,  found  in  the  heavy,  waxy  lands.  The 
disease,  so  far,  is  restricted  only  to  Texas,  New  Mexico, 
Oklahoma,  and  Arizona,  where  it  also  attacks  the  cot- 
ton, okra,  cowpeas,  beans,  apples,  pears,  grapes,  mul- 
berry, castor  beans  and  many  other  economic  crops.  The 
loss  from  Texas  root  rot  varies  with  the  season.    Fre- 


i62  The  Sweet  Potato 

quent  showers  during  July  and  August  greatly  favor  the 
disease. 

Symptoms.  Viewed  from  afar,  an  infected  field  ap- 
pears promising.  It  is  only  during  harvesting  that  the 
extent  of  loss  is  appreciated.  Not  all  hills  are  destroyed, 
since  the  disease  works  in  irregular  spots,  the  size  of 
which  will  vary  from  that  of  a  single  hill  to  a  quarter  of 
an  acre  or  more.  The  causal  organism  usually  attacks 
the  plant  at  its  crown  or  through  the  underground 
parts  and  works  up  a  few  inches  to  the  main  stem.  The 
vines  die  only  at  the  invaded  area,  as  new  roots  are  sent 
out  at  the  nodes.  During  digging,  there  are  usually  very 
few  or  no  potatoes  at  each  diseased  hill.  The  affected 
roots  are  firm,  soggy,  and  brown.  The  few  sound  pota- 
toes which  may  be  obtained  from  a  diseased  hill  will  not 
keep  very  long,  but  will  usually  rot  from  the  entrance 
of  secondary  organisms. 

The  Organism.  Ozonium  omnivorum  is  propagated 
from  year  to  year  mostly  by  its  vegetative  mycelium 
which  winters  over  on  living  roots  of  sweet  potato, 
cotton,  okra,  or  on  perennial  susceptible  weeds.  The 
sweet  potato,  especially,  is  a  favorable  host  on  which  to 
winter  over,  as  the  causal  organism  is  seen  to  grow 
luxuriantly  on  the  remaining  living  roots  in  the  soil 
during  any  time  in  the  winter.  The  mycelium  of  O. 
omnivorum^  is  brown,  septate,  and  branched,  the 
branches  being  nearly  at  right  angles.  The  hyphae  may 
frequently  be  seen  on  the  surface  of  the  dead  stems  or 
roots  as  grayish  wefts  of  mycelial  strands.  These 
strands  are  made  up  of  interwoven  mycelial  threads. 
The  causal  organism  occasionally  produces  conidia  in 
the  field  and  when  grown  in  pure  culture  In  the  labora- 
tory. So  far,  every  effort  by  the  author  to  germinate 
these  conidiospores  has  failed.     For  this  reason,  it  is 


Specific  Diseases  163 

difficult  as  yet  to  ascribe  the  function  of  these  spores  in 
the  life  cycle  of  the  causal  organism. 

Control.  Where  root  rot  is  prevalent,  sweet  potatoes 
should  not  be  planted  on  heavy  clay  soils,  but  only  on 
sandy  or  sandy  loams.  Deep  clean  cultivation,  aeration 
of  the  soil,  and  rotation  with  grain  crops  In  which  clean 
culture  is  practiced  will  help  to  keep  the  disease  in  check. 

Rhizoctonia  Root  Rot 
Caused  by  Rhizoctonia  sp. 

Rhizoctonia  root  rot  is  a  hot-bed  disease.  It  fre- 
quently occurs  where  the  soil  in  the  frame  was  fertilized 
heavily  with  manure.  The  disease  is  manifested  as  deep 
brown  lesions  or  cankers  at  the  foot  of  the  plant.  These 
lesions  are  often  deep  enough  for  the  affected  sprouts  to 
break  in  two  when  touched  or  when  being  watered. 

Control.  Rhizoctonia  root  rot  may  be  kept  in  check 
by  filling  the  hot-bed  with  clean  sand  instead  of  heavily- 
manured,  rich  clay  soil.  As  a  further  precaution,  the 
seed  sweet  potatoes  should  be  treated  with  corrosive  sub- 
limate. 

Other  Fungi 

Several  organisms  have  been  isolated  by  Harter  (51) 
from  rotted  sweet  potatoes  which  were  as  follows: 
Nectria  ipomeae  Hals.,  which  grows  only  on  sweet  po- 
tatoes rotted  by  other  organisms;  Fusarium  caudatum 
Woll,  which  is  not  parasitic.  Among  others  in  which 
parasitism  has  not  been  tested  out  may  be  mentioned  the 
following:  Zygorhynchus  sp.,  Penicillium  sp.  (Fig. 
19,  m),  Melanospora  sp.,  Trichosporium  sp.,  Ceratos- 
toma  sp.,  Sporotrichium  sp.,  Pestalozzia  sp.,  Aspergillus 


l64  The  Sweet  Potato 

niger  Von  Tiegh,  Fusarium  vasinfcctum  Atk.,  Cepha- 
lothecium  sp.,  Neosomospora  vasinfectum  Atk.,  Verti- 
cillium  cinnaharinus,  Acromoniella  sp.,  Macrosporium 
sp.,  Actinomyces  sp.,  and  others. 


Non-Parasitic  Diseases 

Hollow  Heart 

Caused  by  drought 

Hollow  heart  Is  a  new  disease  of  the  sweet  potato.  As 
far  as  is  known  to  the  author,  this  trouble  has  not  been 
reported  before  in  literature.  It  was  especially  preval- 
ent in  Texas  during  19 18.  The  summer  in  that  year 
was  unusually  dry,  the  sweet  potatoes  had  made  scant 
growth,  and  the  yields  were  below  the  average.  The 
sweet  potatoes  when  harvested  were  practically  cured. 
When  the  crop  was  put  in  storage,  the  farmers  again  put 
it  through  the  regular  curing  process,  in  which  case  more 
moisture  was  given  off.  Specimens  wh-en  received  and 
broken  open,  were  found  to  be  hollow  in  the  center,  and 
the  flesh  dry  and  pithy.  When  cross-sections  of  various 
potatoes  were  made,  it  became  evident  that  the  trouble 
resided  in  the  fibro-vascular  bundles,  which  were 
cracked  and  disintegrated.  As  the  potatoes  were  cut 
farther  down,  the  cracks  became  more  and  more  prom- 
inent and  on  reaching  the  center,  the  heart  of  the  root 
was  found  to  be  hollow  (Fig.  20,  a).  Numerous  cul- 
tures of  the  potatoes  affected  with  hollow  heart  yielded 
no  organism.  With  the  Irish  potato,  hollow  heart  is 
attributed  to  prolonged  drought,  followed  by  excessive 
rain.    With  the  sweet  potato,  hollow  heart  seems  to  be 


Specific  Diseases  165 

favored  by  a  prolonged  dry   season   followed   by  the 
usual  curing  in  storage. 

Control  It  is  at  once  evident  that,  during  dry  sea- 
sons, the  roots  contain  naturally  less  moisture  when  har- 
vested. Under  these  conditions,  the  curing  period 
should  be  short,  and  the  potatoes  subjected  to  no  high 
temperature  which  is  conducive  to  more  rapid  sweating. 


Net  Necrosis 

Cause  Unknown 

Net  necrosis  in  the  sweet  potato  resembles  the  same 
disease  in  the  Irish  potato.  The  symptoms  are  prac- 
tically alike  in  both.  The  disease  appears  as  dark 
brown  streaks  at  the  vascular  bundles  (Fig.  20,  b),  and 
may  often  be  mistaken  for  the  browning  brought  about 
by  vine  wilt,  Fusarium  hatatatis,  and  F.  hyperoxy- 
sporum.  These  streaks  originate  at  the  point  of  attach- 
ment to  the  vine.  Frequently  it  may  not  be  detected  at 
time  of  digging,  but  the  streaking  will  develop  later  in 
storage.  The  cause  of  net  necrosis  is  not  known.  Re- 
search along  this  line  Is  very  desirable. 

Mosaic 

Cause  Unknown  * 

This  disease  is  as  yet  of  little  economic  importance. 
It  was  first  described  by  Ensign  (22)  and  by  Rosen 
(85)  in  Arkansas.    The  writer  has  seen  this  disease  in 

♦Recently,  Ray  Nelson  (Pkytopath,  13:9,  1923)  has  indicated  that 
mosaic  in  plants  is  probably  induced  by  protozoa,  apparently 
trypanosomes,  or  closely  related  to  this  genus. 


i66  The  Sweet  Potato 

Georgia  and  in  Texas,  but  not  in  sufficient  quantity  to 
attract  the  general  attention. 

The  symptoms  are  characteristic  of  mosaic.  The 
affected  foliage  is  mottled,  dwarfed,  and  poorly  de- 
veloped.   Diseased  hills  produce  few  or  no  potatoes. 

Control.  The  disease  may  be  eradicated  if  care  is 
taken  not  to  use  seed  (roots)  from  infected  hills.  These 
should  be  pulled  out  and  destroyed.  Two  successive 
seasons  of  careful  roguing  of  diseased  plants  will  prob- 
ably eliminate  all  infected  seed. 


CHAPTER  XIII 

INSECT  AND  OTHER  PESTS 

In  a  work  of  this  nature,  consideration  of  the  im- 
portant insect  pests  of  sweet  potatoes  can  not  be  over- 
looked. 

SwEET  Potato  Weevil 

The  information  on  the  sweet  potato  weevil  is  taken 
from  Chittenden  (12).  The  losses  from  the  weevil 
often  vary  from  25  to  50  per  cent  and  in  numerous  cases 
the  crop  is  a  total  failure.  In  19 17,  in  Texas  the  sweet 
potato  crop  was  valued  at  $9,000,000.00.  The  loss  from 
the  weevil  was  20  per  cent  or  $1,800,000.00  for  that 
year.  In  Louisiana  with  a  crop  valued  at  $5,000,000.00, 
losses  in  191 7  amounted  to  about  12  per  cent  or  $600,- 
000.00,  Florida,  with  a  $4,000,000  crop  lost  about 
$400,000.00. 

Sources  of  Infestation.  According  to  Chittenden  the 
principal  infestation  comes  through  over-wintered  wee- 
vils. These  live  over  winter,  in  storage  houses  on  stored 
sweet  potatoes,  and  oh  roots  left  in  the  field  after  dig- 
ging. The  weevil  is  further  carried  on  cuttings,  vines, 
draws,  and  slips,  and  especially  seed  roots  as  well  as 
o;i  morning  glories. 

Distribution.  The  weevil  is  known  to  occur  in 
Florida,  Louisiana,  Texas,  Georgia,  Mississippi  and 
Alabama.  Should  it  ever  be  found  in  Tennessee,  it  will 
167 


i68  The  Sweet  Potato 

spread  rapidly  to  North  and  South  Carolina,  Missouri, 
Kentucky,  Oklahoma  and  Arkansas.  Unless  drastic 
measures  are  taken  by  both  State  and  Federal  Govern- 
ments, the  weevil  may  spread  to  every  state  in  the  Union 
where  this  crop  is  grown.  The  weevil  is  also  found  in 
Cochin  China,  Mauritius,  India,  Asia,  Africa,  Formosa, 
Madagascar,  Australia,  Hawaii,  Guam,  West  Indies, 
Cuba,  Porto  Rico,  Haiti,  Grand  Cayman,  Jamaica  and 
British  Guiana. 

Food  Habits  and  Nature  of  Injury.  The  sweet  po- 
tato weevil  feeds  on  the  sweet  potato,  the  yam,  the 
goat's-foot  morning  glory  (Ipomoea  pes-capra),  and 
other  plants  of  the  Morning  Glory  family. 

The  weevil  feeds  on  the  sweet  potato  leaves,  vines, 
stalks  and  roots.  The  female  weevil  lays  her  eggs  in  the 
vines  and  in  the  stalks  or  crowns  as  well  as  in  the  roots 
and  continues  to  work  and  breed  in  the  roots  in  storage. 
The  larvae,  on  hatching,  feed  and  tunnel  through  the 
vines  to  the  roots,  in  which  case  the  vines  are  killed 
and  the  roots  become  badly  riddled  and  filled  with  ex- 
creta which  imparts  such  a  bitter  taste  that  even  swine 
will  not  eat  them.  Frequently,  enough  eggs  are  de- 
posited at  the  base  of  the  vine  so  that  when  the  larvae 
hatch,  they  completely  girdle  the  plant.  The  sweet  po- 
tato weevil  has  a  pair  of  delicate  looking  wings  which 
are,  however,  little  used;  hence  it  can  not  be  supposed 
that  its  spread  is  due  primarily  to  flight.  Its  spread  is 
largely  made  possible  through  the  shipment  of  infested 
seeds  and  plants. 

Control.  All  states  in  which  sweet  potato  weevil  are 
known  to  occur  should  adopt  quarantine  measures. 
Such  are  already  in  force  in  Georgia,  Florida  and  Ala- 
bama. In  Texas,  the  quarantine  legislation  prohibits  the 
transportation  of  sweet  potato  plants,  draws,  and  slips 


Insect  and  Other  Pests  169 

from  a  weevil-Infested  locality  to  regions  where  the 
insect  Is  unknown.  For  the  further  prevention  of  the 
spread  of  this  pest  it  is  necessary  to  clean  up  infested 
fields  as  promptly  as  possible  and  to  destroy  all  vines  and 
all  other  remnants.  Then  the  ground  should  be  deeply 
plowed  and  kept  free  from  volunteer  sweet  potatoes  or 
morning  glory  vines.  It  is  a  good  policy  to  have  the 
field  gone  over  by  hogs  after  harvesting,  and  this  will 
usually  clean  up  all  the  culls  and  strings.  A  further  con- 
trol measure  is  crop  rotation.  Corn,  cotton,  tobacco, 
Irish  potatoes  or  any  other  truck  crop  except  sweet  po- 
tatoes should  be  planted  after  sweet  potatoes.  All  new 
fields  should  be  planted  far  from  the  original  seed  bed. 

Where  sweet  potatoes  are  only  lightly  infested  by  the 
weevil,  they  are  sometimes  disinfected  and  the  insects 
destroyed  by  carbon  disulphide  evaporated  in  tight  re- 
ceptacles. Where  this  is  done,  however,  the  roots  usually 
lose  their  germinating  powers  and  fail  to  sprout,  or,  as 
is  often  the  case,  may  rapidly  decay.  From  our  present 
meager  knowledge  it  is,  therefore,  not  advisable  to  fumi- 
gate sweet  potatoes.  Spraying  the  foliage  with  one  pint 
of  zinc  arsenlte  in  40  gallons  of  water  will  reduce  the 
damage  from  weevils  sometimes  about  80  per  cent. 
Where  this  is  used,  fifteen  pounds  of  cactus  solution 
should  be  added  to  each  40  gallons  of  the  spray  mixture 
to  help  it  stick  and  spread  better.  The  spray  should  be 
applied  as  soon  as  the  first  weevils  appear.  A  second 
application  should  also  be  made,  and  a  third  one  in  case 
of  heavy  infestation.  Before  the  plants  are  set  out  in 
the  field,  they  should  also  be  dipped-  In  a  solution  com- 
posed of  one  pound  of  lead  arsenate  and  10  gallons  of 
water. 

The  best  method  to  prevent  the  spread  of  the  weevil 
is  legislation.    The  following  samples  of  proclamations 


170  The  Sweet  Potato 

by  the  United  States  Secretary  of  Agriculture  are  self- 
explanatory. 

Sweet  Potato  and  Yam  Quarantine  (Foreign)^ 
Notice  of  Quarantine  No.  29 

The  fact  has  been  determined  by  the  Secretary 
of  Agriculture,  and  notice  is  hereby  given,  that 
certain  injurious  insects,  new  to  and  not  heretofore 
widely  prevalent  or  distributed  within  and  through- 
out the  United  States,  namely,  sweet  potato  weevils 
(Cylas  spp.),  occur  in  Cuba,  Haiti;  Jamaica,  British 
Guiana,  India,  China,  Cochin  China,  Friendly 
Islands,  Sumatra,  Formosa,  Philippine  Islands, 
Australia,  Madagascar,  and  Liberia,  and  the  sweet 
potato  scarabee  (Eiiscepes  hatatae),  occurs  in  the 
Barbados,  Antigua,  Nevis,  St.  Vincent,  St.  Kitts, 
Jamaica,  Brazil,  New  Zealand,  and  Guam. 

Now,  therefore,  I Secretary  of 

Agriculture,  under  the  authority  conferred  by  the 
act  of  Congress  approved  August  20,  19 12,  known 
as  the  Plant  Quarantine  Act  {2^y  Stat,  315),  do 
hereby  declare  that  it  is  necessary,  in  order  to  pre- 
vent the  introduction  into  the  United  States  of  the 
sweet  potato  weevils  and  the  sweet  potato  scarabee 
mentioned  above,  to  forbid  the  importation  into  the 
United  States  from  the  above-named  and  all  other 
foreign  countries  and  localities  of  all  varieties  of 
sweet  potatoes  and  yams  {I porno ea  batatas  and 
Dioscorea  spp.). 

On  and  after  January  i,  19 18,  and  until  further 
notice,  by  virtue  of  said  act  of  Congress  approved 
August  20,  1912,  the  importation  for  any  purpose 
of  any  variety  of  sweet  potatoes  or  yams  {Ipomoea 
batatas  and  Dioscorea  spp. )  from  the  above-named 
and  all  other  foreign  countries  and  localities  is  pro- 


Insect  and  Other  Pests  171 

hibited,  except  for  experimental  or  scientific  pur- 
poses by  the  Department  of  Agriculture ;  provided, 
that  the  entry  for  immediate  export,  or  for  im- 
mediate transportation  and  exportation  in  bond,  of 
sweet  potatoes  and  yams  (Ipomoea  batatas  and 
Dioscorea  spp.)  of  all  varieties  designated  in  this 
quarantine  may  be  permitted  in  accordance  with  the 
regulations  governing  such  entry  for  immediate  ex- 
port, or  for  immediate  transportation  and  exporta- 
tion in  bond,  promulgated  by  the  Secretary  of  Agri- 
culture, October  20,  19 17. 

This  notice  of  quarantine  shall  not  apply  to  the 
Territories  of  Hawaii  and  Porto  Rico. 

Done  in  the  District  of  Columbia  this  i8th  day 
of  December,  191 7.  Witness  my  hand  and  the 
seal  of  the  United  States  Department  of  Agricul- 
ture. 

(Signed) 

Secretary  of  Agriculture. 


Sweet  Potato  and  Yam  Quarantine  (Domestic) 

Notice  of  Quarantine  No.  30 

The  fact  has  been  determined  by  the  Secretary 
of  Agriculture,  and  notice  is  hereby  given,  that  two 
injurious  insects,  namely,  the  sweet-potato  weevil 
(Cylas  formicarius)  and  the  sweet-potato  scarabee 
(Euscepes  batatae),  new  to  and  not  heretofore 
widely  prevalent  or  distributed  within  and  through- 
out the  United  States,  exist  in  the  Territories  of 
Hawaii  and  Porto  Rico. 

Now,  therefore,  I, Secretary  of 

Agriculture,  under  the  authority  conferred  by  the 
act  approved  August  20,  19 12,  known  as  the  Plant 
Quarantine  Act  (37  Stat.,  315),  do  hereby'quar- 


172  The  Sweet  Potato 

antine  said  Territories  of  Hawaii  and  Porto  Rico, 
and  do  prohibit,  by  this  Notice  of  Quarantine  No. 
30,  the  movement  from  the  Territories  of  Hawaii 
and  Porto  Rico  into  or  through  any  other  Terri- 
tory, State,  or  District  of  the  United  States  of  all 
varieties  of  sweet  potatoes  and  yams  {Ipomoea 
batatas  and  Dioscorea  spp.) 

On  and  after  January  i,  19 18,  and  until  further 
notice,  by  virtue  of  said  act  of  Congress  approved 
August  20,  19 12,  it  shall  be  unlawful  to  move  any 
sweet  potatoes  or  yams  (Ipomoea  batatas  and 
Dioscorea  spp.),  of  any  variety  from  the  Terri- 
tories of  Hawaii  and  Porto  Rico  into  or  through 
any  other  Territory,  State,  or  District  of  the 
United  States,  regardless  of  the  use  for  which  the 
same  are  intended. 

This  quarantine  shall  not  apply  to  the  movement 
by  the  United  States  Department  of  Agriculture 
of  the  plant  products  named  for  experimental  or 
scientific  purposes. 

Done  in  the  District  of  Columbia  this  i8th  day 
of  December,  191 7. 

Witness  my  hand  and  the  seal  of  the  United 
States  Department  of  Agriculture. 


(Signed)  

Secretary  of  Agriculture 


Flea  Beetle 

(Chaetocnema  confinis  Cr.) 

The  sweet  potato  flea  beetles  are  small,  brownish- 
black  insects.  They  eat  their  way  through  the  leaves 
forming  small  channels.  As  a  result,  many  of  the 
leaves  of  the  young  plants  are  killed,  turn  brown,  and 


Insect  and  Other  Pests  173 

rot.  They  are  especially  severe  on  low  land,  and  where 
sweet  potatoes  are  grown  a  number  of  years  on  the 
same  land. 

Control.  Sanderson  recommends  dipping  the  plant 
before  putting  it  out  in  the  field  in  a  solution  of  arsenate 
of  lead.  An  application  of  ordinary  Bordeaux  mixture 
will  act  as  a  repellant. 

Tortoise  Beetles 

These  are  small,  brilliant,  golden  colored  beetles,  be- 
longing to  the  family  Cassidae.  They  are  beautiful  little 
insects  with  a  peculiar  power  of  changing  color.  Some 
of  the  species  even  appear  like  drops  of  molten  gold. 
The  beetles  usually  feed  on  the  foliage,  causing  round 
holes.  The  leaves  are  often  so  riddled  as  almost  to 
destroy  the  value  of  thd  plant. 

Control.  The  methods  advised  for  the  control  of  flea 
beetles  may  also  apply  to  the  tortoise  beetle. 

Termite  Injury 

Sweet  potato  injury  from  termites  or  white  ants 
is  often  serious  during  dry  seasons.  The  injury  from 
termite  may  often  be  confused  with  that  from  the  sweet 
potato  weevil.  Berger  (3)  emphasizes  the  distinguish- 
ing characteristics  of  the  damage  caused  by  white  ants 
as  follows : 

1.  Absence  of  larvae  (grubs)  and  pupae  in  the  tun- 
nels when  infested  by  termites,  but  their  presence  in 
apparent  abundance  when  the  tuber  is  infested  with  the 
weevil. 

2.  Absence  of  frass  (excreta)  when  the  Injury  is  due 
to  termites,  but  an  abundance  of  this  in  the  tunnels  pro- 
duced by  the  weevil. 


174  The  Sweet  Potato 

3.  Exit  and  entrance  holes  very  apparent  with  ter- 
mites, but  tuber  infested  with  weevil  may  show  little  or 
no  outward  evidence  of  its  condition  inside. 

4.  The  clean-cut  outlines  of  the  tunnels  made  by  the 
termites  are  in  marked  contrast  with  those  made  by  the 
weevil  (Fig.  20,  c). 

Besides  the  differences  indicated  in  the  illustrations, 
several  other  facts  .of  use  in  determining  the  presence  of 
the  weevil  or  termites  may  be  noted : 

5.  If  the  plants  are  growing,  tunneling  larvae 
(grubs)  in  the  stems  near  the  ground  indicate  the  weevil. 

6.  The  presence  of  large  (about  %  in.  long)  ant-like 
insects  with  black  heads  and  snout,  brick-red  thorax 
(middle)  and  legs,  and  dark  steel-blue  hind  end,  is  an 
almost  certain  sign  of  the  weevil. 

7.  The  presence  of  whitish  rapidly  running  insects, 
having  much  the  appearance  of  ants,  indicates  termites. 


Root  Knot 

Caused  by  Heterodera  radickold  (Greef)  Mull. 

Root  knot  of  sweet  potatoes  is  commonly  found  in 
the  Southern  States  in  light  sandy  soils.  It  is  charac- 
terized by  small  swellings  on  the  lateral  feeding  roots. 
This  disease,  although  serious  on  numerous  other  crops 
in  the  sandy  soils,  does  not  seem  to  injure  the  sweet 
potato  to  any  great  extent.  Root  knot  is  very  severe  on 
the  cowpea  and  the  okra;  hence  in  small  farms,  crops 
which  are  susceptible  to  root  knot  should  be  avoided,  as 
otherwise  the  little  nematode  worms  will  be  greatly  in- 
creased in  the  soil. 


0  @  0   0 


c.  Hollow  heart, 
caused  by  termite. 


Fig.  2o. 

b.   Net  necrosis, 
(c  after  Ber^jer.) 


Varioi's  Diseases. 

c.  Sweet  potatoes  showinj,'  tunnels 


Insect  and  Other  Pests  175 

Rat  and  Mice  Injury 

These  pests  are  often  troublesome  in  the  storage 
houses.  They  feed  on  sweet  potatoes  by  nibbhng  on 
them,  thereby  opening  the  way  to  soft  rot  and  many 
other  diseases.  The  best  way  to  control  these  rodents 
is  to  soak  wheat  or  corn  in  a  solution  of  one  ounce  of 
strychnine  sulphate  dissolved  in  one-half  pint  of  water. 
The  grain  may  be  soaked  for  twenty-four  hours  and 
then  distributed  to  various  parts  of  the  house  where  rats 
and  mice  may  get  it.  Large  quantities  of  the  grain  may 
be  soaked  in  the  poison,  and  then  dried  and  kept  for 
future  use.  In  every  case,  the  poison  should  be  care- 
fully labeled  and  the  poisoned  grain  protected  in  such 
a  way  that  no  chickens  or  any  other  farm  animals  may 
have  access  to  it.  In  sweet  potato  houses  with  floor  ven- 
tilators the  opening  to  these  ventilators  should  be 
screened  with  a  ^-inch  galvanized  wire  cloth  so  that 
it  will  be  impossible  for  rats  and  mice  to  enter. 


PART  III 
STORAGE  METHODS 


CHAPTER  XIV 

METHODS  OF  STORING  SWEET  POTATOES 

In  the  first  two  parts  of  this  work  we  have  been  con- 
cerned with  methods  of  producing  a  good  sweet  potato 
crop,  free  from  disease.  When  this  is  done,  what  comes 
next?  Of  all  the  vegetable  food  products,  none  is  more 
perishable  than  the  sweet  potato.  There  is  very  little  or 
no  profit  derived  when  the  sweet  potato  is  dumped  on 
the  market  at  harvesting,  because  at  that  time,  the  mar- 
kets are  often  glutted,  and  the  prices  low.  The  best 
prices  are  obtained,  and  the  highest  profit  attained,  when 
the  sweet  potatoes  are  put  away  in  storage  during  the 
winter  months  and  sold  to  the  best  markets  at  that  time. 
The  final  success  with  sweet  potatoes  directly  depends 
on  how  well  this  crop  can  be  stored. 

There  are  several  ways  of  storing  sweet  potatoes, 
namely,  dehydration,  canning,  storing  in  banks,^  and 
storing  in  drying  houses  popularly  known  as  "Kiln 
dryers." 

Dehydration 

By  dehydration  is  here  meant  the  drying  of  the  sweet 
potato  so  as  to  remove  most  of  its  moisture  (Fig.  21, 
a  and  b  compared).  The  process  as  far  as  it  applies  to 
sweet  potatoes  is  only  in  its  infancy,  and  the  industry  if 
properly  developed  may  have  a  great  future.  With  this 
method,  the  losses  from  rot  could  be  wiped  out  alto- 
gether. The  principle  of  dehydration  is  by  no  means 
179 


i8o  The  Sweet  Potato 

new;  however,  present-day  methods  are  decidedly  dif- 
ferent from  early  methods,  as  they  are  more  improved 
and  practical. 

Dehydrated  sweet  potatoes,  to  command  a  market, 
must  not  have  their  starch  and  other  substances  de- 
stroyed by  scorching  or  burning.  By  proper  manipula- 
tion, however,  the  food  value,  the  quality,  and  the 
flavor  may  be  conserved  well.  It  should  be  remembered 
that  sweet  potatoes,  like  any  other  plants,  are  made  up 
of  cells.  These  may  be  compared  to  extremely  thin 
walled  boxes  or  sacks  separated  by  small  interspaces. 
These  boxes  or  cells  are  filled  with  the  stored-up  food 
materials.  Any  method  of  dehydration  must  aim  to 
preserve  intact  the  cellular  structure  of  the  sweet  potato, 
and  permit  the  equal  evaporation  of  water  from  the  en- 
tire inner  content.  Dehydration,  to  be  successful,  must 
not  be  so  unevenly  and  rapidly  done  as  to  dry  and  form 
an  outer  shell  or  skin ;  neither  should  the  temperature  be 
so  high  as  to  transform  all  the  cellular  contents. 

Dehydration  on  a  commercial  basis  dates  from  the 
Boer  war.  At  that  time,  the  British  needed  large  quan- 
tities of  dried  foods  for  shipment  to  their  troops  in 
South  Africa.  This  product  was  obtained  from  Canada 
where  large  dehydration  plants  were  established.  At 
the  close  of  the  war,  the  manufacturers  had  large  quan- 
tities on  hand  which  remained  unused  by  the  British 
army.  This  supply  was  packed  in  barrels,  sealed  with 
paraffin  and  kept  until  the  recent  World  War,  when  it 
was  used  again  by  the  British  army  in  France. 

In  the  United  States,  dehydration  until  recent  years 
was  progressing  rather  slowly.  The  investigations  of 
the  Bureau  of  Chemistry,  United  States  Department  of 
Agriculture,  have  given  this  industry  much  impetus 
through  the  leadership  of  Major  S.  C.  Prescott  (82). 


Fig.  21.    Stor.-xgk  Methods. 
a.  One  bushel  of  sweet  potatoes  before   dehydration.     /;.  TIk 


same  after 
after 
)mpson.) 
„.  Construction  of  a  sweet  potaio  oanK  gaiter  iv    v..  w.i.,.     ...„,.ct  POtato 
banks  in  the  field  (after  H.  C.  Thompson).    /.  CapiMns,-.     g.  Tippmg  sweet 
potato  cans.     (/  and  g  after  E.  T.  Miller.) 


dehydration,  showing  shrinkage  due  to  loss  of  water.  "^  ^  ^i"'  '' 
S.  C.  Prescott.)  c.  Simple  cellar  storage  house  after  H.  L.  lliom 
d.  Construction  of  a  sweet  potaio  bank  (after  R   G.  Hill),     t-.  Sweet  j 


Methods  of  Storing  Sweet  Potatoes     i8i 

There  are  several  methods  of  dehydrating  vegetables, 
which  apply  equally  to  the  sweet  potato. 

1.  Tunnel  Process.  In  this  method,  a  narrow,  long 
tunnel  structure  is  heated  by  numerous  coils  or  steam 
pipes  horizontally  laid.  The  tunnel  is  provided  with 
holders,  or  screened  receptacles;  these  are  perforated 
trays  to  hold  the  product  to  be  dehydrated.  Through 
this  turmel  is  blown  a  blast  of  hot  air  which  takes  up 
the  air  from  the  moist  product.  This  method  is  greatly 
improved  by  the  use  of  dampers  which  regulate  the  flow 
of  air.  The  objection  to  this  system  is  that  the  product 
may  become  overheated  or  scorched,  and  the  food  value 
impaired. 

2.  Kiln  Process.  This  system  is  used  in  New  York 
and  in  California.  It  was  originally  adopted  for  curing 
hops.  This  type  consists  of  a  chamber  with  a  perforated 
floor  through  which  heated  air  rises  from  a  furnace. 
The  material  to  be  dried  is  spread  on  the  floor  and 
turned  several  times  to  obtain  uniform  dryness.  The 
main  drawback  in  this  method  is  the  high  cost  of  opera- 
tion. 

3.  Vacuum  Process.  In  this  method  the  air  is  sucked 
out  by  vacuum  in  the  same  way  in  which  chemicals  or 
liquids  are  dried.  This  method  is  poorly  adapted  to 
dehydrate  vegetables,  because  the  product  loses  its  food 
value  and  quality. 

Dehydrated  sweet  potatoes  are  prepared  In  the  same 
way  as  Irish  potatoes ;  that  is,  they  are  cut  into  flakes  or 
slices  with  the  same  kind  of  machine. 

The  potatoes  are  first  placed  in  a  washer  In  which  the 
whole  potatoes  are  thoroughly  washed  in  water  with 
paddles.  From  the  washer,  the  potatoes  are  transferred 
to  bins  by  means  of  elevated  hoppers.  From  the  bins, 
they  are  fed  Into  the  cooker.    The  potatoes  are  then 


i82  The  Sweet  Potato 

steamed  in  the  cooker,  which  has  a  capacity  of  about 
800  pounds  and  is  emptied  every  half  hour.  From  the 
cooker,  they  are  transferred  into  a  trough  with  a  ribbon 
conveyer  which  pumps  them  into  the  hopper  above  the 
drying  cyHnders,  at  the  same  time  breaking  them  thor- 
oughly. Inside  of  the  hopper,  the  potatoes  are  mashed 
considerably  between  the  upper  parts  of  the  two  cylin- 
ders. 

The  cylinder  dryers  consist  of  two  heavy  hollow- 
cast  cylinders  each  six  feet  long  and  three  feet  in 
diameter.  These  have  a  smooth  surface  and  are  heated 
by  steam.  The  two  cylinders,  though  parallel,  work  in- 
dependently of  each  other.  When  revolving,  each  cylin- 
der becomes  coated  with  a  layer  of  cooked  potatoes. 
The  thickness  of  the  coat  is  regulated  by  small  rollers 
set  closely  against  the  surface  of  the  large  cylinder.  The 
heat  in  the  hollow  cylinder  quickly  dries  the  coat  of 
mashed  potatoes.  By  that  time,  the  revolving  cylinders 
are  set  against  knives  which  scrape  off  the  coating.  The 
product  is  dry  and  breakable  and  looks  like  thin  crepe 
paper.    These  are  the  sweet  potato  flakes. 

Sweet  Potato  Flour.  The  flakes  as  they  are  dropped 
into  a  trough  are  sucked  into  a  large  pipe  by  means  of  a 
strong  fan.  From  the  pipe,  the  flakes  are  thrown  into 
a  collector,  whence  they  slide  down  to  a  mill  and  are 
pulverized  into  flour. 

Neither  dehydrated  sweet  potatoes  nor  sweet  potato 
flour  have  as  yet  been  offered  commercially  on  markets 
at  home  or  abroad.  These  two  products,  however,  pre- 
sent new  industries  with  a  great  future.  The  process  of 
dehydrating  sweet  potatoes  will  solve  the  storage  prob- 
lem and  will  reduce  all  losses  from  rots.  Excepting 
diseased  stock,  all  grades  of  sweet  potatoes,  even  the 
culls,  could  be  utilized  for  that  purpose  and  there  would 


Methods  of  Storing  Sweet  Potatoes    183 

be  no  waste.  With  this  method,  too,  large  quantities  of 
dried  sweet  potatoes  could  be  sold  and  shipped  to  many 
of  the  European  countries.  It  has  been  estimated  that  a 
bushel  of  fresh  sweet  potatoes  weighs  about  46  pounds, 
■which  after  dehydration  weighs  10  pounds.  It  is  thus 
seen  that  we  economize  36  pounds  in  freight  by  elim- 
inating water  only.  Dehydrated  sweet  potatoes  may 
keep  indefinitely  if  properly  protected  from  insect  in- 
jury. When  ready  to  be  cooked  they  have  to  be  soaked 
in  water,  and  the  same  water  is  used  again  in  cooking. 

Canning  Sweet  Potatoes  * 

Canning  was  not  known,  until  1806,  when  an  Eng- 
lishman by  the  name  of  Laddington  first  found  that 
food  put  in  closed  containers  and  heated  would  keep  in- 
definitely. In  1 8 10,  Nicholas  Appert,  a  Frenchman  was 
the  first  to  obtain  a  patent  on  this  process. 

Sweet  potato  canning  has  of  late  assumed  an  im- 
portant economic  aspect  in  New  Jersey,  Delaware, 
Maryland,  Virginia,  and  in  many  southern  states. 

Excepting  diseased  material,  canning  sweet  potatoes 
affords  means  of  utilizing  all  grades,  even  culls,  and  of 
reducing  all  losses  from  rots.  The  canned  product  is 
palatable,  and  in  most  respects  as  acceptable  as  freshly 
cooked,  stored  sweet  potatoes.  It  will  keep  almost  in- 
definitely, and  may  be  shipped  anywhere  in  the  world. 

Blanching.  By  blanching  is  here  meant  the  plunging 
of  the  sweet  potato  in  boiling  water  for  several  minutes. 
This  is  done  to  remove  adhering  dirt,  and  eliminate  any 
objectionable  taste. 

Capping.    The  steps  in  this  process  are  as  follows: 

*  See  also ;  Magoon,  C.  A.  and  Culpepper,  C.  W.  "A  study  of  sweet 
potato  varieties  with  special  reference  to  their  canning  quality. "  U.S. 
Dept.  of  Agr.  Bui.  1041:1-34,  1922. 


i84  The  Sweet  Potato 

The  cap  is  placed  over  the  opening  and  the  soldering 
fluid  or  flux  (also  known  as  zinc  chloride)  is  applied 
with  a  small  brush.  Then  a  hot  capping  steel  is  held  to 
the  solder-rimmed  cap  until  the  solder  is  melted  and  fills 
the  groove  in  which  the  cap  fits.  The  steel  is  turned 
around  a  few  times  and  the  rod  that  runs  through  the 
center  pressed  down.  This  rod  is  sufficiently  long  to 
allow  the  capper  to  be  raised  from  the  cap  without  re- 
leasing the  pressure  on  the  cap  by  the  rod.  The  steel 
should  be  lifted  for  an  instant  to  allow  the  solder  to  set 
before  removing  the  center  rod  from  the  can  (Fig.  21, 
f  andg). 

Exhausting.  This  means  the  driving  out  of  surplus 
air  from  the  can.  It  is  easily  accomplished  by  adding  a 
little  boiling  water  to  the  can  before  capping. 

Tipping.  This  is  soldering  the  vent  hole,  to  seal  the 
can  completely. 

Processing.  This  is  the  final  cooking  or  sterilizing  of 
the  sealed  can. 

Cooling.  As  soon  as  the  cans  are  taken  out  of  the 
steam  cooker,  they  should  be  cooled  by  being  dipped  in 
cold  water.  All  cans  after  processing  should  be  care- 
fully tested  for  leaks. 

Sweet  potatoes  can  be  canned  successfully  under 
steam  pressure  only.  There  are  two  ways  of  packing; 
one  where  the  whole  potato  is  packed  dry,  the  other 
where  the  potatoes  are  first  cooked  to  a  pulp  and  then 
packed.  The  varieties  best  suited  for  canning  are  the 
Yellow  Yam,  Yellow  Jersey,  Pumpkin  or  Dooley  Yam, 
Southern  Queen,  Big  Stem  Jersey,  Triumph,  and  Nancy 
Hall.  When  No.  3  cans  are  used,  the  packed  cans  are 
sterilized  eighty  minutes  at  240  degrees  F.  When  No. 
10  cans  are  used  the  packed  cans  are  sterilized  for  two 
and  one  half  hours  at  240  degrees  F. 


Methods  of  Storing  Sweet  Potatoes     185 

Storage  in  Banks  and  in  Cellars 

Storage  in  Banks.  This  is  perhaps  the  crudest  and 
oldest  method  of  storing.  It  is  still  in  vogue  to-day  in 
the  South,  but  it  is  being  gradually  replaced  by  properly 
constructed  storage  houses. 

Construction  of  Banks.  Banks  (Fig.  21,  d  and  c) 
should  be  located  on  well-drained  land.  Stagnant 
water  will  ruin  the  potatoes.  It  is  necessary  to  make  the 
bottom  of  the  bank  level.  The  size  will  vary  greatly.  It 
is,  however,  preferable  to  construct  several  small  banks 
instead  of  one  or  two  large  ones.  Ordinarily  the 
diameter  of  the  bank  varies  from  6  to  10  feet.  It  is 
necessary  to  dig  two  small  trenches  across  the  floor  at 
right  angles  to  each  other.  This  will  provide  the  neces- 
sary means  of  ventilation.  The  two  trenches  are  cov- 
ered with  boards  or  wooden  troughs.  At  the  junction 
where  the  trenches  cross,  a  loosely  nailed  4-by-4-inch 
box  is  set  in  to  form  a  flue  up  through  the  potatoes,  its 
height  that  of  the  middle  height  of  the  bank.  It  is  ad- 
visable to  have  the  four  sides  of  the  wooden  flue  per- 
forated with  holes  to  assist  further  in  the  ventilation  of 
the  bank.  The  earth  floor  of  the  bank  is  covered  with  a 
4-  or  6-inch  layer  of  straw,  hay,  dry  leaves,  or  pine 
needles,  and  the  potatoes  placed  in  a  conical  pile  around 
the  flue  (Fig.  21,  d).  The  potato  pile  is  then  covered 
with  hay  and  old  corn  stalks  and  allowed  to  remain  in 
this  condition  as  long  as  the  weather  is  favorable.  This 
will  encourage  evaporation  of  the  excessive  moisture. 
As  soon  as  it  turns  colder,  the  outer  cover  of  straw  and 
corn  stalks  is  overlaid  with  5  to  6  inches  of  soil. 
The  openings  of  the  floor  trench  of  the  ventilators,  and 
of  the  flue  are  not  shut  as  long  as  there  is  no  danger  of 
freezing. 


i86  The  Sweet  Potato 

The  disadvantages  In  storing  in  banks  are:  large  loss 
due  to  decay;  inferior  quality  of  the  sound  potatoes,  due 
to  lack  of  curing;  loss  on  the  market,  because  banked 
potatoes  rot  soon  after  being  moved;  inconvenience  of 
getting  the  potatoes  during  cold,  rainy  weather. 

Barre  (2)  claims  that  in  South  Carolina  sweet  pota- 
toes keep  just  as  well  in  banks  as  in  regular  storage 
houses.  This  claim,  however,  is  based  on  one  year's  ex- 
periment with  forty-five  bushels  stored  in  three  banks. 
As  a  rule,  banked  potatoes  will  keep  fairly  satisfactorily 
in  favorable  seasons.  When  we  consider  the  results  in 
a  period  of  years,  the  losses  are  heavy.  With  our  pres- 
ent knowledge  on  sweet  potato  storage  houses  there  is 
hardly  any  excuse  for  storing  in  banks,  especially  when 
the  crop  is  destined  to  be  marketed. 

Storage  in  Cellars.  In  the  South,  sweet  potatoes  are 
often  stored  in  a  cellar-like  structure  (Fig.  21,  c).  It  is 
constructed  of  a  line  of  posts  through  the  center,  sup- 
porting a  ridgepole.  Upon  this  pole  and  the  ground  on 
each  side,  the  ends  of  the  planks  are  placed.  The  ends 
of  the  enclosure  are  boarded  up,  a  door  being  provided 
in  one  end.  The  structure  is  covered  with  sod  to  a 
thickness  of  6  inches.  Such  a  structure  is  only  permis- 
sible where  sweet  potatoes  are  grown  for  home  use.  In 
this  case  it  is  more  advantageous  than  banks.  This  cellar 
may  also  be  improved  by  having  two  doors,  one  at  each 
end,  and  a  ventilator  in  the  roof.  This  will  permit  more 
ventilation.  A  slat  floor  raised  five  inches  from  the 
ground,  upon  which  the  potatoes  may  be  placed,  is  an  ad- 
ditional improvement. 

In  the  North,  in  some  parts  of  Delaware,  under- 
ground cellars  are  built  to  store  seed  sweet  potatoes  over 
winter.  A  pit  8X10X8  feet  is  dug,  and  the  floor  as 
well  as  the  walls  up  to  the  ground  level  are  built  of  con- 


Methods  of  Storing  Sweet  Potatoes    187 

Crete.  The  roof  and  the  entrance  to  the  cellar  are  built 
above  ground.  A  fire  is  maintained  in  a  small  stove 
during  curing,  as  well  as  later  to  prevent  freezing. 
Ventilation  is  obtained  through  the  ventilator  in  the 
roof,  and  through  the  door  in  the  front.  The  potatoes 
are  stored,  either  in  hampers,  or  in  small  bins,  con- 
structed at  each  side. 


CHAPTER  XV 

PHYSIOLOGICAL  CHANGES  DURING  STORAGE 

The  reason  so  many  have  failed  and  given  up  in 
despair  is  that  sweet  potato  storage  has  not  as  yet  been 
placed  on  a  scientific  basis.  Every  grower,  every  buyer, 
and  every  storer  of  sweet  potatoes  has  his  own  theories, 
practices,  and  pet  beliefs.  There  is  yet  no  uniform 
standard  to  go  by.  The  whole  industry  has  been  a  hit- 
or-miss  proposition.  Practices  which  in  one  year  have 
yielded  fair  results  have  proved  a  total  failure  another 
year.  For  this  reason,  all  modest  and  intelligent  sweet 
potato  growers  agree  that  the  older  they  get  and  the 
more  they  deal  with  sweet  potatoes,  the  less  they  know 
about  storing  this  crop.  The  same  attitude  is  current 
among  scientific  people.  Sweet  potato  storage  has 
proved  a  treacherous  problem.  The  difficulty  in  the  past 
has  been  that  investigators  who  worked  on  sweet  potato 
storage  have  neither  studied  the  diseases  nor  the  physi- 
ology of  the  sweet  potato  in  all  its  aspects,  but  have 
busied  themselves  merely  with  devising  a  house.  The 
pathologist  on  the  other  hand  gave  little  attention  to  any 
other  phase  except  diseases. 

The  work  of  Messrs.  Hasselbring  and  Hawkins  (53)", 
of  Harter  (42)  and  Weimer  (no  and  in),  which  is 
only  a  beginning  in  this  direction,  will  no  doubt  help  to 
explain  many  things  which  until  recently  have  seemed 
very  obscure.    It  will  be  difficult  to  treat  the  subject  of 


Physiological  Changes  189 

storage  without  first  considering  the  physiological  and 
chemical  changes  which  take  place  in  the  sweet  potato 
from  the  time  it  is  harvested  and  stored,  until  it  is  ready 
for  shipment. 

The  greatest  loss  of  sweet  potatoes  in  storage  is  due 
to  decay  caused  by  microorganisms  which  invade  the 
tissue.  Chemical  and  physiological  changes  in  the  root 
no  doubt  play  an  important  role  in  predisposing  the 
host  to  decay.  This  in  brief  brings  us  to  a  considera- 
tion of  the  carbohydrate  metabolism  of  the  sweet  potato 
in  storage. 

To  determine  this,  Hasselbring  and  Hawkins  (53) 
used  two  varieties,  the  Big  Stem  Jersey,  representing  the 
sugary  type,  and  the  Southern  Queen,  the  starchy  type. 
Fifteen  bushels  of  each  were  stored.  Nine  crates  of 
each  were  subjected  for  ten  days  to  "sweating"  or  cur- 
ing at  a  temperature  of  2^  degrees  C.  (equivalent  to 
about  81  degrees  F.).  After  sweating,  the  temperature 
was  dropped  to  the  regular  storage  temperature  ranging 
from  45  to  60  degrees  F.  The  remaining  six  crates  of 
each  were  placed  in  cold  storage  where  the  temperature 
was  maintained  at  4  degrees  C.  (38  degrees  F.).  The 
data  of  the  seasonal  changes  of  the  potatoes  stored  in 
the  cold  storage  room  and  of  those  kept  under  ordinary 
storage  conditions  are  shown  in  Tables  24  and  25. 

From  Table  24  it  is  seen  that  under  normal  storage 
conditions  the  moisture  content  of  the  root  remains 
fairly  constant.  This  does  not  mean  that  there  is  no 
moisture  lost  during  "sweating,"  and  during  the  re- 
maining part  of  the  storage  season.  The  loss  of  moisture 
is  here  compensated  by  the  water  formed  by  respira- 
tion. The  old  belief  that  the  sweet  potato  lost  all  its 
necessary  moisture  during  "sweating"  is  no  longer 
tenable. 


190 


The  Sweet  Potato 


2 

•8 
1 

1 
1 

1 

.6.0 

1 

III 

if 

MiiMMU 

00JCCJ««2 

1" 

t^t^I^l^vO  O  O  fOVO   •^00  t^oo  11  O  t>. 

"^^ 

O  VO   lO  lO  lOOO   lO  Tj-  <N 

M    C»  VO    ITlM 

1 

+ 

6        6 
+        + 

l-l 

+ 

Gain 
or  Loss 

of 

Starch 

(as 

Glucose)  1 

: 

VO 

CO 

1 

CO           Tj- 

lO              TJ- 

d          d 
1            1 

1 

s 

Total 
Carbo- 
hydrates 

as 
Glucose 

o 
■* 
N 

00 

to           to 

M 

to 

Total 
Sugar 

as 
Glucose 

1 
1 

% 

w 

8 

m          ON 

00 

Reducing 
Sugar 

as 
Glucose 

s 

1 

d 

O             00 

? 

i 

^ 

Jo 
to 

CO             •<*• 

vd 

1 

a 
1 

On 

vd 

^       8 

vd         vd 

M                     l-l 

ti 

i 

g. 
^ 

00             o 

00 

i4 

00 

i 

Dec.    6 
Jan.     4 

1 

Physiological  Changes  191 


2^^ 

rfMoo  «r»weo  ION 

M    M    W                     M    C, 

g^^j?g?;r'^ 

a 

wt>.'«a-ooMwov  r^oo  vo  os  on  n  m  m 

WVO 

« 

8. 

& 

0 
+ 

0 

1 

M 

1 

0 

+ 

0 

1 

to 

% 

2" 

a 

l^ 

■* 

1 

0 
+ 

+ 

0 
1 

$ 

CO 

f: 

^ 

0 

J? 

S! 

^ 

J? 

^ 

^ 

^ 

^ 

s 

00 

t>. 

VO 

t^ 

I^ 

^ 

0 

<5^ 

a 

<3^ 

HI 

HI 

0 

0 

0 

% 

^ 

vS 

? 

10 

00 

VO 

vO 

>o 

NO 

10 

g^ 

5 

^ 

8 

>2 

JO 

CO 

Tf 

^ 

HI 

S; 

8 

^ 

<J^ 

i? 

«% 

J5 

?l 

R 

?i. 

« 

g 

^ 

VO 

•H 

1 

^ 
^ 

!3 

1 

t— > 

ovo  coo  ^^r^ 

woo  tOMOO  IC« 

M    (V 

M    HI    N                     HI    M 

^iil 

^88gslgggg| 

0;3^:2;^QQQQAAAA 

t^t^r^l^vO  0  0  c^vo  rhoo  t^oo 

VO  HI  VO  VO  \r>m  tooo  uo  •rh  «  w  r» 

C^CIMMMWHIHIMHIHIHIM 

7 

10 

^ 

s> 

W 

0 

0 

+ 

+ 

+ 

t^ 

CO 

0 

■^ 

VO 

10 

I 

0 
1 

0 

+ 

00 

VO 

»o 

HI 

8 

■* 

VO 

10 

10 

VO 

^ 

N 

W 

c< 

w 

Oi 

rt- 

OS 

VO 

vO 

■<t 

Tj- 

s 

HI 

CO 

Tt- 

■* 

^ 

?^ 

•i! 

ON 

r^ 

w 

10 

t^ 

t>. 

t>. 

t^ 

0 

0 

0 

0 

o\ 

i>. 

0 

CO 

HI 

o\ 

^ 

N 

CO 

CO 

ON 

!>. 

0 

10 

0 

00 

CO 

N 

Ov 

ON 

ON 

N 

5^ 

5- 

^ 

to 

HI 

00 

1^ 

t^ 

t^ 

VO 

VO 

VO 

CO 

0 

t>. 

„ 

HI 

^ 

1 

a 

1 

192 


The  Sweet  Potato 


Week 
ending 
Jan.  28 
Feb.     5 
Feb.  12 
Feb.  19 
Feb.  26 

^«oojowcojorjONNOcoor>.co 

^         wOt^CNtt^rJ-OOwwON  t^OO  NO  On  On  N  w  « 

^"^  <0  JO  M  rj  NO 

•*  10  »ONO  NOOONOt^OOOOOI^ww 

Gain 
or  Loss 

of 

Sugar 

(as 

Glucose)^ 

Grams 

+0.29 

+0.05 

ON                           VO                             t^ 
«                              Tl-                            10 

^66 

1                              +                               1 

1 

, 

Cain 
or  Loss 

of 

Starch 

(as 

Glucosey 

Grams 
-0.59 

—0.26 

►H                              CO                            M 

ir>             NO               -"t 
►h'              d              d 
+               1               + 

^  1 

Total 
Carbo- 
hydrates 

as 
Glucose 

Per  Cent. 
26.11 

25.90 

r<                 »o                ON 

N                     0                    00 

NO                          NO                           10 

www 

Total 
Sugar 

as 
Glucose 

Per  Cent. 
4-75 

4.80 

NO                         O"                       S» 
CO                   •*                   CO 

1^ 

Reducing 
Sugar 

as 
Glucose 

Per  Cent. 
0.60 

0.53 

(N)                                 W                                 10 

10              »o              10 

6            6            6 

1 

ii 

Per  Cent. 
3-95 

4.05 

CO                    ON                    0 
On                   CO                  00 

ci               CO              ci 

« 
& 

i 

Per  Cent. 
19.22 

18.99 

^      %      ]f^ 

8          2^          8 

1 

1 

Per  Cent. 
68.02 

68.00 

l-l                              HI                             10 

i       i      i 

1 

i4 

Feb.     3 
Feb.  28 

April    8 
May    4 
June    4 

Physiological  Changes  193 

It  is  interesting  to  note  that  the  percentage  of  starch 
shows  a  sudden  decrease  immediately  after  the  potatoes 
were  harvested.  The  subsequent  decrease  is  more 
gradual,  and  continues  until  a  minimum  is  reached  in 
March.  From  that  time  on  the  percentage  of  starch 
rises  again.  In  proportion  as  there  is  a  decrease  in  the 
starch,  there  is  a  corresponding  increase  in  sugar. 

The  causes  of  the  changes  in  the  percentage  of  cane 
sugar  follow  that  of  the  total  sugar.  In  the  Southern 
Queen,  after  the  first  rise,  it  decreases  continuously.  In 
the  Big  Stem,  the  invert  sugar  shows  a  distinct  maxi- 
mum. 

The  data  in  Table  24  indicate  that  sweet  potatoes  rot 
in  storage  in  proportion  as  the  starch  decreases  and  is 
changed  into  sugar.  The  secret  of  proper  storage  would 
be  to  determine  the  best  conditions  which  would  favor 
the  increase  of  sugar  to  the  extent  of  giving  the  stored 
potato  its  quality,  and  at  the  same  time  prevent  it  from 
rotting. 

From  Table  25  it  is  seen  that  three  lots  of  potatoes 
were  used.  One  of  the  Big  Stem,  and  another  of  the 
Southern  Queen  were  placed  in  cold  storage  after  they 
had  been  cured.  The  third  lot  of  Big  Stem  were  kept 
in  warm  storage  until  March  27,  and  at  that  date  trans- 
ferred to  cold  storage.  The  storage  experiments  were 
of  short  duration,  because  the  potatoes  kept  only  six 
weeks,  and  then  rotted. 

The  data  in  Table  25  show  that  at  low  temperatures 
the  starch  disappears  and  is  replaced  by  an  accumula- 
tion of  sugar  much  faster  than  under  warm  storage  con- 
ditions. This  would  indicate  the  reason  why  sweet  po- 
tatoes rot  in  cold  storage.  Harter  (51)  has  shown  that 
under  low  temperatures,  sweet  potatoes  are  rotted  by 
certain  organisms  which  apparently  are  unable  to  work 


194 


The  Sweet  Potato 


I 


11 

fcovo  ceo  t^Tj-i-ioo  m 

t 

00  OVOVO   rJ-'4-^ON  t'500 

Gain 
or  Loss 

of 
Sugar 

{as 
Glucose) 

1 

:       5             ^ 

fo                 d 
+                + 

Gain 
or  Loss 

of 
Starch 

(as 
Glucose) 

c3 

1                         1 

Total 
Carbo- 
hydrates 

as 
Glucose 

8 

lO              N                           i-i 

00              vo                           CO 

Total 
Sugar 

as 
Glucose 

1 
1 

lO                    00                                          6^. 

Reducing 
Sugar 

as 
Glucose 

1 
1 

jl 

1 
■5 

►e 
jj 

3 
1 

1 

1 

1 

Nov.    8 
Dec.    9 

Dec.  21 

Physiological  Changes  195 


: 

:     : 

10 

CO 

0 

+ 

VO 

CO 

0 

1 

r^ 

00 

■* 

M 

« 

C» 

N 

ON 

rl- 

fO 

NO 

00 

„ 

" 

^ 

^ 

M 

w 

rh 

■<t 

VO 

00 

On 

ON 

t^ 

0 

0^ 

" 

On 

w 

to 

CO 

l>. 

t>. 

r^ 

0 

N 

^ 
S 

1 

5?a^:?S?7^ 

MOO  io 

HI    1-1    N 

00  NVOVO 

Th  Tj- Tj- On  rooo 

l^t^JOiO'+'^TttOfON 

S 

fO 

' 

+ 

+ 

^ 

s 

N 
1 

T 

% 

NO 

00 

^ 

VO 

NO 

S' 

<^ 

'g 

to 

NO 

1^ 

^ 

ON 

^ 

0 

0 

0 

s^ 

s 

ON 

0 

10 

VO 

00 

^ 

% 

On 

^ 

NO 

5- 

£5 

00 

NO 

^ 

NO 

2 

00 

CI 

1 

a 

i 

S3   fe 


m    t/J" 


s  s 


^1 


.2^ 


q3  <43 


196  The  Sweet  Potato 

under  higher  temperatures.  The  current  belief  of 
growers  is  that  sweet  potatoes  freeze  at  about  40  de- 
grees F.  From  the  above  data  and  the  work  of  Harter 
(51)  it  is  evident  that  the  sweet  potato  does  not  freeze 
at  that  temperature,  but  that  the  starch  is  rapidly  dis- 
placed by  cane  sugar,  and  at  this  stage,  the  potato  be- 
comes susceptible  to  attacks  of  various  fungi.  The 
temperatures  at  which  sweet  potatoes  would  actually 
freeze  is  as  yet  unknown.  This  is  an  important  con- 
sideration from  the  carriers'  point  of  view.  Sweet 
potatoes  are  often  damaged  in  transit,  and  the  shipper 
attributes  such  damage  to  freezing. 

A  jury  may  rightly  ask  the  question  as  to  what  is  a 
frozen  sweet  potato.  Evidently,  in  the  past,  we  have 
had  no  clear  distinction  between  a  rotted  and  a  frozen 
sweet  potato. 

From  the  data  presented  above,  it  is  very  evident  that 
the  starch  in  stored  sweet  potatoes  is  first  converted  to 
reducing  sugar  and  this  is  synthesized  to  cane  sugar. 
Since  it  is  the  sugar  in  the  sweet  potato  that  predisposes 
it  to  rot,  it  is  necessary  from  the  viewpoint  of  keeping 
quality  to  know  at  what  temperature  the  greatest  change 
takes  place.  The  experiments  by  Hasselbring  and  Haw- 
kins (53)  are  very  enlightening,  although  their  work 
is  based  on  a  very  short  storage  period.  They  found 
that  at  30  degrees  C.  (86  degrees  F.),  the  greater  part 
of  the  cane  sugar  is  formed  during  the  first  10  to  12 
days  after  the  roots  have  been  harvested.  This  is  prac- 
tically true  of  sweet  potatoes  kept  at  15  degrees  C.  (59 
degrees  F.).  However,  at  5  degrees  C.  (40  degrees  F.) 
the  rate  of  the  transformation  of  the  starch  into  sugar 
is  slower,  but  the  reaction  is  continuous.  This  is  why, 
after  six  weeks  in  a  cold  storage  room,  there  is  so  much 
sugar  and  so  little  starch  found  in  the  roots.    This  seems 


Physiological  Changes  197 

to  explain  why  sweet  potatoes  rot  so  rapidly  under  low 
temperatures.  More  extended  investigations  of  the 
effect  of  temperature  on  the  conversion  of  starch  into 
sugar  under  normal  storage  is  very  imperative.  More 
definite  information  along  these  lines  will  help  to  solve 
the  storage  problem  of  sweet  potatoes. 

It  has  already  been  indicated  that  in  stored  sweet  po- 
tatoes the  starch  disappears,  and  is  replaced  by  cane  and 
reducing  sugars.  From  the  investigations  of  Hassel- 
bring  and  Hawkins  (53)  it  appears  that  the  reducing 
sugars  supply  the  source  of  respiratory  material.  The 
cane  sugar,  it  seems,  is  relatively  stable.  Once  this  is 
formed,  it  is  not  readily  utilized  in  the  process  of  res- 
piration of  the  sweet  potato.  During  respiration,  the 
reducing  sugars  are  converted  into  water  and  carbon 
dioxide.  Temperature  seems  to  influence  the  amount  of 
respiration. 


CHAPTER  XVI 

THE  CURING  PERIOD 

There  are  many  farmers  in  the  South  who  still  per- 
sist in  storing  sweet  potatoes  in  banks,  believing  that 
there  are  some  mysterious  ways  about  curing  sweet  po- 
tatoes in  houses  which  are  not  wholly  within  the  reach 
of  the  average  man.  Just  how  this  feeling  came  about 
is  hard  to  explain.  By  curing  sweet  potatoes  is  meant 
driving  out  the  excess  moisture  from  the  roots  as  they 
are  brought  in  from  the  field,  to  enable  them  to  keep 
better  and  for  a  longer  time  than  they  otherwise  would. 
Sweet  potatoes  may  be  kept  over  winter  without  curing, 
but  such  potatoes  will  not  stand  shipment,  and  are  in- 
ferior in  taste  when  cooked.  For  home  markets  or 
where  the  crop  has  to  be  shipped  to  reach  its  market,  it 
must  be  put  through  the  curing  period.  In  banks,  this 
process  can  not  possibly  be  carried  out  except  occasion- 
ally under  unusually  favorable  weather.  Curing  in  the 
storage  house  may  be  accomplished  by  artificial  heat  and 
ventilation.  The  heat  creates  air  currents  in  the  house 
and  aids  in  drying  the  potatoes.  The  methods  of  heat- 
ing are  considered  on  page  213. 

Temperature 

Much  guesswork  is  as  yet  attached  to  the  required 
temperature    necessary    for    curing.      Experience    has 
taught  blindly  that  heat  is  necessary  for  curing  sweet 
198 


The  Curing  Period 


199 


potatoes.  Every  manager,  however,  has  his  own  pet 
theories  about  temperatures.  In  much  of  the  sweet  po- 
tato literature  a  temperature  of  90  to  100  degrees  F.  is 
recommended.  Some  writers  advocate  that  the  storage 
house  should  be  closed  from  ten  to  fifteen  days  during 
the  storage  period.  If  this  is  carried  out  literally,  a 
large  percentage  of  the  crop  will  soft-rot.  Potatoes 
seldom  keep  well  if  they  are  heated  up  to  100  degrees  F. 
with  all  the  doors  and  windows  of  the  house  shut.  The 
high  temperature  and  moisture  conditions  would  favor 
soft  rot  and  black  rot.  On  the  other  hand,  if  the  pota- 
toes are  given  all  the  ventilation  possible  during  curing, 
it  is  difficult  to  maintain  the  temperature  of  the  house  at 
90  to  100  degrees  F.,  as  the  heat  will  escape.  This  is 
especially  true  under  conditions  in  New  Jersey  or  Dela- 


Table  26 

Temperature  and  Moisture  Studies  at  the  Delaware  House 

October,  igi4 


First  Floor  East 

Second  Floor  East 

Third  Floor  East 

Date 

Temper- 

Relative 

Temper- 

Relative 

Temper- 

Relative 

ature 

Humidity 

ature 

Humidity 

ature 

Uumidity 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

26 

75 

75 

60 

74 

76 

67 

65 

75 

5.^ 

27 

5,S 

60 

50 

55 

66 

66 

60 

45 

66 

64 

62 

.^0 

28 

5» 

6,^ 

63 

60 

62 

55 

63 

66 

64 

65 

65 

.30 

29 

60 

64 

65 

60 

6.^ 

66 

70 

60 

64 

65 

60 

.35 

30 

66 

62 

45 

20 

65 

66 

60 

40 

64 

65 

55 

20 

31 

60 

65 

65 

40 

64 

68 

65 

50 

65 

70 

50 

35 

200 


The  Sweet  Potato 


Table  26 — {Continued) 
November,  IQ14 


/"tVi/  77/oor  Eorf 

Second  Floor  East 

Third  Floor  East 

Date 

Temper- 

Relative 

Temper- 

Relative 

Temper- 

Relative 

ature 

Humidity 

ature 

Humidity 

ature 

Humidity 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

I 

66 

88 

65 

60 

68 

70 

70 

65 

72 

65 

55 

40 

2 

66 

68 

70 

35 

68 

70 

75 

36 

70 

68 

55 

55 

3 

64 

66 

65 

45 

65 

58 

70 

50 

60 

65 

60 

25 

4 

68 

72 

65 

50 

70 

60 

75 

50 

60 

68 

65 

30 

60 

66 

60 

25 

66 

68 

60 

45 

68 

68 

60 

5 

6 

60 

65 

60 

50 

66 

68 

60 

55 

66 

66 

55 

35 

7 

58 

66 

60 

55 

62 

68 

60 

50 

66 

64 

70 

30 

8 

68 

70 

65 

60 

70 

73 

65 

60 

70 

68 

50 

35 

9 

64 

64 

60 

50 

66 

65 

60 

55 

64 

68 

60 

50 

10 

58 

62 

55 

50 

62 

65 

50 

50 

66 

62 

60 

50 

II 

63 

64 

55 

50 

65 

66 

60 

55 

68 

60 

50 

45 

12 

58 

63 

60 

50 

62 

66 

60 

55 

68 

62 

60 

40 

13 

64 

68 

65 

50 

66 

68 

65 

55 

68 

62 

55 

25 

14 

65 

66 

60 

50 

66 

68 

65 

55 

68 

64 

55 

40 

15 

68 

70 

70 

75 

70 

72 

70 

75 

70 

70 

65 

80 

16 

72 

66 

73 

60 

74 

70 

75 

65 

66 

74 

70 

45 

17 

60 

58 

50 

45 

64 

62 

55 

40 

62 

60 

45 

20 

18 

55 

54 

60 

55 

60 

62 

60 

50 

66 

62 

55 

35 

19 

58 

60 

65 

65 

63 

65 

65 

70 

65 

64 

60 

50 

20 

60 

60 

67 

60 

64 

65 

67 

62 

65 

64 

60 

37 

21 

58 

54 

58 

50 

62 

63 

60 

55 

65 

62 

45 

30 

22 

58 

58 

62 

60 

62 

63 

62 

60 

63 

60 

50 

48 

23 

53 

52 

62 

50 

58 

60 

60 

50 

62 

60 

58 

30 

24 

50 

54 

57 

58 

56 

60 

57 

52 

60 

58 

53 

40 

25 

55 

58 

62 

60 

60 

64 

60 

60 

64 

56 

50 

47 

26 

56 

64 

65 

62. 

1 

66 

65 

62 

68 

60 

58 

35 

27 

60 

64 

67 

65 

67 

70 

62 

66 

62 

58 

45 

28 

56 

62 

63 

62 

66 

70 

65 

65 

62 

57 

45 

29 

63 

64 

67 

68 

60 

60 

68 

62 

65 

64 

60 

55 

30 

66 

68 

75 

70 

64 

66 

75 

70 

65 

68 

62 

62 

The  Curing  Period 


201 


Table 

26— 

{Continued) 

December,  1914 

First  Floor  East 

Second  Floor  East 

Third  Floor  East 

Date 

Temper- 

Relative 

Temper- 

Relative 

Temper- 

Relative 

ature 

Humidity 

ature 

Humidity 

ature 

Humidity 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

I 

67 

68 

75 

75 

70 

72 

77 

75 

70 

71 

65 

60 

2 

67 

70 

75 

80 

70 

72 

75 

77 

70 

72 

68 

^5 

3 

70 

68 

75 

73 

73 

74 

77 

80 

72 

75 

70 

^5 

4 

66 

68 

67 

72 

70 

70 

75 

70 

70 

70 

67 

60 

70 

68 

65 

65 

70 

68 

65 

68 

70 

70 

62 

57 

6 

65 

68 

60 

62 

66 

68 

67 

65 

66 

65 

62 

63 

7 

64 

66 

65 

63 

66 

68 

72 

70 

66 

66 

65 

55 

8 

65 

64 

70 

72 

68 

68 

70 

75 

68 

70 

65 

60 

9 

64 

63 

72 

70 

66 

66 

70 

65 

68 

66 

65 

70 

lO 

64 

65 

67 

66 

66 

66 

67 

65 

65 

68 

65 

60 

II 

62 

62 

65 

70 

65 

66 

67 

72 

66 

68 

67 

58 

12 

62 

53 

58 

50 

64 

63 

67 

55 

61 

64 

60 

50 

13 

57 

60 

57 

63 

60 

64 

60 

65 

58 

58 

63 

65 

14 

62 

62 

60 

58 

64 

64 

62. 

60 

60 

62 

63 

§° 

15 

52 

56 

40 

60 

57 

60 

55 

52 

50 

56 

68 

65 

16 

50 

56 

48 

60 

55 

60 

55 

55 

58 

60 

58 

45 

17 

50 

57 

50 

65 

54 

60 

55 

55 

57 

62 

45 

35 

18 

50 

54 

55 

65 

54 

58 

60 

63 

56 

62 

35 

32 

19 

52 

56 

62 

65 

56 

60 

62 

60 

58 

62 

40 

45 

20 

56 

56 

62 

60 

60 

60 

65 

60 

60 

58 

50 

42 

21 

56 

57 

65 

72 

58 

60 

68 

65 

58 

60 

50 

55 

22 

54 

56 

57 

62 

57 

60 

65 

55 

58 

60 

50 

47 

23 

53 

54 

60 

50 

55 

60 

60 

60 

i 

60 

42 

^o 

24 

50 

50 

45 

48 

56 

58 

60 

55 

5^ 

45 

48 

25 

54 

53 

50 

47 

58 

58 

55 

52 

56 

58 

53 

40 

26 

48 

52 

40 

45 

52 

55 

60 

55 

50 

54 

55 

35 

27 

47 

50 

45 

50 

52 

55 

55 

55 

52 

54 

48 

40 

28 

47 

52 

50 

50 

52 

56 

50 

57 

54 

54 

42 

40 

29 

52 

54 

50 

50 

56 

60 

60 

50 

54 

56 

55 

55 

30 

54 

55 

55 

55 

60 

60 

60 

55 

58 

58 

56 

62 

31 

52 

52 

55 

60 

58 

58 

60 

60 

52 

56 

50 

45 

202 


The  Sweet  Potato 


Table  26 — (Continued) 
Jamiary,  IQ15 


First  Floor  East 

Second  Floor  East 

Third  Floor  East 

Date 

Temper- 

Relative 

Temper- 

Relative 

Temper- 

Relative 

ature 

Humidity 

ature 

Humidity 

ature 

Humidity 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M 

P.M. 

I 

50 

52 

55 

62 

56 

58 

60 

65 

54 

55 

45 

48 

2 

50 

56 

58 

50 

54 

60 

67 

50 

55 

56 

40 

50 

3 

51 

53 

55 

60 

54 

58 

55 

63 

52 

56 

40 

35 

4 

51 

53 

63 

60 

55 

58 

65 

50 

54 

54 

33 

50 

50 

56 

60 

57 

55 

61 

63 

55 

52 

60 

45 

57 

6 

55 

60 

60 

60 

60 

65 

65 

60 

56 

64 

50 

55 

7 

64 

64 

60 

50 

66 

68 

67 

65 

64 

66 

62 

55 

8 

58 

60 

62 

55 

60 

62 

67 

65 

58 

60 

50 

50 

9 

58 

62 

62 

55 

60 

64 

70 

60 

58 

58 

50 

50 

10 

54 

56 

55 

60 

58 

62 

50 

63 

54 

62 

52 

45 

II 

52 

56 

58 

60 

58 

62 

50 

60 

54 

58 

55 

50 

12 

62 

63 

60 

60 

64 

66 

72 

70 

62 

62 

68 

70 

13 

62 

66 

55 

53 

64 

68 

70 

65 

54 

64 

70 

60 

14 

60 

64 

65 

58 

64 

68 

70 

70 

60 

65 

60 

63 

15 

64 

66 

67 

50 

66 

70 

67 

65 

62 

67 

65 

60 

16 

60 

64 

60 

57 

64 

66 

70 

65 

58 

60 

60 

58 

^l 

63 

66 

57 

60 

64 

70 

65 

67 

18 

72 

75 

63 

63 

74 

77 

72 

57 

19 

75 

64 

65 

45 

78 

68 

76 

55 

20 

64 

64 

50 

57 

66 

66 

57 

60 

21 

60 

62 

50 

45 

62 

64 

55 

55 

22 

54 

60 

45 

50 

60 

64 

55 

40 

23 

58 

62 

50 

55 

63 

66 

57 

60 

24 

56 

56 

43 

45 

60 

60 

55 

55 

25 

58 

60 

65 

55 

62 

64 

65 

66 

26 

56 

58 

50 

58 

58 

60 

65 

60 

27 

58 

60 

65 

58 

62 

65 

67 

28 

56 

56 

65 

60 

58 

60 

65 

65 

29 

51 

54 

40 

60 

56 

60 

53 

70 

30 

5d 

52 

50 

60 

56 

58 

70 

70 

31 

50 

52 

60 

65 

54 

58 

65 

70 

[The  Curing  Period 


203 


Table  26 — (Continued) 
February,  igis 


F*V5f  Floor  East 

Second  Floor  East 

Third  Floor  East 

Date 

Temper- 

Relative 

Temper- 

Relative 

Temper- 

Relative 

ature 

Humidity 

ature 

Humidity 

ature 

Humidity 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

I 

50 

58 

60 

65 

54 

58 

65 

70 

2 

54 

58 

65 

70 

58 

66 

70 

75 

3 

56 

56 

64 

67 

60 

60 

72 

75 

4 

52 

50 

53 

50 

56 

54 

65 

62 

5 

48 

50 

50 

55 

52 

54 

60 

57 

6 

47 

50 

50 

67 

52 

55 

65 

7 

54 

56 

70 

67 

58 

62 

70 

70 

8 

48 

5^ 

56 

55 

54 

54 

65 

65 

9 

45 

4^ 

47 

50 

50 

52 

60 

55 

10 

42 

48 

40 

50 

47 

52 

53 

55 

II 

42 

49 

55 

50 

47 

55 

65 

55 

12 

49 

54 

50 

55 

54 

60 

55 

55 

13 

54 

53 

50 

55 

57 

58 

55 

65 

14 

51 

55 

63 

70 

55 

62 

73 

70 

IS 

56 

60 

70 

72 

62 

68 

70 

72 

16 

58 

56 

68 

70 

62 

60 

70 

75 

17 

52 

52 

60 

63 

54 

56 

70 

65 

18 

44 

48 

45 

55 

47 

52 

60 

60 

19 

42 

48 

55 

50 

^o 

54 

60 

55 

20 

42 

50 

50 

55 

48 

56 

55 

55 

21 

48 

57 

55 

60 

45 

53 

55 

45 

22 

50 

58 

57 

57 

46 

52 

52 

50 

23 

53 

61 

57 

62 

50 

58 

58 

60 

24 

60 

62 

65 

68 

57 

60 

57 

65 

25 

58 

59 

63 

50 

56 

54 

60 

56 

26 

52 

56 

40 

38 

50 

52 

48 

50 

27 

48 

52 

38 

35 

46 

48 

43 

45 

28 

45 

48 

42 

45 

204 


The  Sweet  Potato 


Table  26 — {Continued) 
March,  IQ15 


Date 

First  Floor 

Temperature 

Relative 
Humidity 

A.M. 

P.M. 

A.M. 

P.M. 

I 

44 

46 

45 

40 

2 

42 

48 

42 

45 

3 

48 

50 

53 

45 

4 

45 

48 

60 

48 

46 

48 

54 

50 

6 

50 

52 

50 

55 

7 

48 

48 

65 

60 

8 

47 

52 

65 

55 

9 

44 

50 

44 

47 

10 

46 

53 

40 

42 

II 

48 

53 

38 

40 

12 

48 

52 

38 

38 

13 

45 

52 

35 

35 

14 

47 

52 

35 

37 

15 

47 

54 

35 

38 

16 

51 

55 

37 

35 

17 

47 

50 

31 

35 

18 

47 

50 

30 

35 

19 

46 

52 

35 

32 

In  order  to  determine  actual  temperature  of  sweet 
potatoes  in  storage,  thermometers  and  hygrometers 
were  installed  in  Delaware  in  a  large  commercial  house 
with  a  capacity  of  forty  thousand  bushels.  Similar  in- 
struments were  installed  and  studies  made  in  Maryland 
in  a  small  house  with  a  capacity  of  eight  thousand 
bushels.  The  Delaware  house  consisted  of  three  floors 
(the  system  of  heating  is  taken  up  on  p.  213).  The 
Maryland  house  had  two  floors  and  was  built  of  brick. 


The  Curing  Period  205 

The  results  are  shown  in  Table  26.  The  readings  were 
taken  at  7  a,  m.  and  6  p.  m. 

In  studying  Table  26  we  see  that  in  a  40,000-bushel, 
3-story  house  in  Delaware,  the  temperature  at  no  time 
went  lower  than  50  degrees  F,  nor  above  75  degrees  F. 
during  the  first  forty  days.  This  is  especially  true  dur- 
ing the  first  fifteen  days  of  the  curing.  Yet  in  that 
house,  there  were  four  stoves  going  full  blast  day  and 
night.  The  heat,  however,  had  a  chance  to  escape,  be- 
cause the  manager  of  that  house,  under  the  author's 
directions,  provided  for  ventilation.  Table  26  there- 
fore, shows  that  under  the  semi-northern  climate  of 
Delaware,  curing  may  be  effected  much  more  advan- 
tageously by  a  medium  temperature,  and  through  an 
abundance  of  ventilation.  Through  this  method  of 
curing,  the  losses  from  rots  at  the  end  of  the  season 
were  kept  down  to  ten  per  cent. 

From  Table  2.^  it  is  seen  that  in  the  2-story,  8000- 
bushel  house  the  temperature  during  sweating,  ranged 
from  50  to  70  degrees  F.,  the  average  being  60  degrees. 
Yet  one  stove  was  burning  all  the  time.  In  this  con- 
nection abundant  ventilation  was  supplied  as  long  as  the 
outdoor  temperature  did  not  go  down  below  60  degrees. 
The  losses  from  rot  in  that  house  were  kept  down  to  8 
per  cent. 

In  the  average  sweet  potato  house,  without  artificial 
methods  of  curing,  it  is  far  more  desirable  to  cure  the 
potatoes  by  all  the  air  currents  (ventilation)  possible, 
even  though  at  a  lower  temperature  (65  to  70  de- 
grees R),  than  overheating  the  house,  and  shutting  out 
all  ventilation. 


206 


The  Sweet  Potato 


Table  27 

Temperature  and  Moisture  Studies  in  the  Maryland  House 

October,  IQ14 


First  Floor 

Top  Floor 

Date 

Temperature 

Temperature 

Moisture 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

28 
29 
30 
31 

t 

60 
64 

11 

58 
58 

60 
60 
60 

66 

60 
60 
50 

55 

20 
20 
30 
10 

November,  IQ14 


I 

64 

68 

62 

72 

55 

15 

2 

66 

70 

62 

72 

55 

15 

3 

66 

68 

64 

64 

50 

20 

4 

66 

72 

64 

72 

50 

30 

5 

68 

66 

66 

66 

50 

31 

6 

64 

66 

62 

66 

40 

20 

7 

60 

64 

58 

60 

45 

20 

8 

62 

68 

60 

68 

40 

9 

60 

66 

60 

68 

80 

40 

10 

60 

62 

58 

62 

50 

10 

II 

58 

60 

54 

60 

50 

40 

12 

58 

62 

54 

64 

55 

10 

13 

60 

68 

60 

64 

45 

30 

14 

62 

64 

62 

64 

50 

45 

15 

64 

68 

64 

66 

60 

80 

I6 

68 

66 

68 

66 

75 

60 

17 

60 

60 

56 

60 

60 

25 

18 

58 

60 

52 

60 

50 

25 

19 

56 

58 

54 

54 

60 

65 

20 

56 

60 

54 

56 

70 

50 

21 

54 

58 

50 

54 

65 

40 

22 

50 

56 

50 

54 

60 

55 

23 

54 

60 

50 

50 

60 

50 

24 

52 

58 

50 

52 

55 

35 

25 

54 

60 

50 

58 

50 

45 

26 

54 

60 

52 

60 

65 

40 

27 

56 

60 

58 

58 

80 

70 

28 

58 

60 

56 

60 

60 

58 

29 

60 

60 

56 

60 

70 

65 

30 

60 

68 

60 

68 

70 

60 

The  Curing  Period 


207 


Table  27 — (Continued) 
December,  1Q14 


/"irrf  Floor 

'  Top  Floor 

Date 

Temperature 

Temperature 

Moisture 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

I 

62 

62 

60 

64 

80 

70 

2 

60 

64 

60 

64 

90 

70 

3 

66 

66 

66 

66 

65 

70 

4 

64 

64 

64 

62 

65 

65 

5 

60 

60 

60 

60 

70 

65 

6 

60 

60 

58 

60 

65 

70 

7 

60 

58 

58 

56 

70 

70 

8 

58 

58 

56 

56 

70 

70 

0 

58 

58 

56 

56 

70 

70 

10 

58 

58 

56 

58 

75 

70 

II 

56 

58 

54 

56 

70 

70 

12 

56 

58 

52 

56 

75 

65 

13 

52 

56 

52 

54 

65 

70 

14 

54 

56 

52 

54 

70 

65 

15 

50 

56 

48 

52 

65 

50 

16 

50 

54 

48 

52 

70 

50 

17 

48 

54 

48 

54 

70 

50 

18 

48 

52 

48 

52 

65 

55 

19 

50 

52 

50 

52 

65 

65 

27 

48 

50 

48 

50 

65 

65 

28 

48 

50 

48 

50 

70 

65 

29 

50 

52 

50 

50 

65 

75 

30 

54 

56 

52 

58 

75 

50 

208 


The  Sweet  Potato 


Table  27 — (Continued) 
January,  igis 


/^tV5<  i?/oor 

Top  Floor 

Date 

Temperature 

Temperature 

Moisture 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

3 

50 

56 

50 

56 

55 

50 

4 

52 

56 

50 

56 

70 

50 

5 

52 

58 

50 

60 

60 

45 

6 

56 

60 

54 

60 

65 

55 

7 

54 

60 

60 

60 

75 

65 

8 

54 

58 

56 

58 

80 

75 

9 

54 

58 

52 

58 

75 

60 

17 

54 

60 

54 

60 

80 

85 

18 

60 

62 

62 

62 

80 

85 

19 

62 

60 

62 

60 

70 

60 

20 

58 

56 

56 

54 

65 

i^ 

21 

54 

54 

52 

52 

70 

65 

22 

54 

56 

54 

54 

65 

60 

23 

52 

58 

54 

58 

65 

65 

24 

54 

54 

54 

54 

70 

70 

25 

54 

54 

54 

52 

65 

70 

26 

54 

56 

52 

58 

65 

60 

27 

54 

56 

54 

56 

65 

65 

28 

56 

56 

54 

54 

70 

60 

29 

50 

54 

50 

54 

65 

60 

30 

50 

50 

50 

54 

54 

65 

31 

50 

54 

52 

50 

50 

50 

The  Curing  Period 


209 


Table  27 — {Continued) 
February,  igis 


i?*>5f  Floor 

Top  Floor 

Date 

Temperature 

Temperature 

Moisture 

A.M. 

P.M. 

A.M. 

P.M. 

A.M. 

P.M. 

I 

52 

60 

50 

54 

60 

60 

2 

62 

60 

52 

62 

75 

60 

3 

54 

54 

62 

60 

60 

65 

4 

52 

50 

54 

54 

70 

65 

5 

50 

52 

52 

5? 

65 

65 

6 

52 

58 

54 

58 

70 

70 

7 

52 

54 

52 

54 

70 

^5 

8 

52 

54 

50 

54 

65 

^J> 

9 

50 

54 

50 

65 

60 

10 

52 

54 

48 

58 

70 

50 

II 

52 

54 

48 

54 

65 

50 

12 

50 

54 

50 

60 

50 

50 

13 

50 

56 

54 

5^ 

60 

65 

14 

54 

58 

54 

58 

60 

60 

15 

56 

60 

54 

62 

75 

65 

16 

60 

58 

62 

58 

55 

60 

17 

52 

54 

52 

56 

60 

60 

18 

52 

58 

50 

56 

55  . 

50 

19 

52 

58 

52 

58 

60 

40 

20 

52 

60 

52 

62 

60 

40 

21 

52 

58 

54 

58 

60 

35 

22 

52 

60 

52 

60 

^5 

40 

23 

54 

60 

54 

62 

60 

40 

24 

58 

58 

58 

58 

r 

70 

25 

54 

54 

54 

52 

80 

70 

26 

50 

60 

50 

56 

65 

40 

27 

52 

56 

50 

^i 

65     50 

28 

52 

54 

52 

56 

60     40 

210 


The  Sweet  Potato 


Table  27 — (Contintied) 
March,  igi5 


A>5f  /^/oor 

Top  Floor 

Date 

Temperature 

Temperature 

Moisture 

\.M. 

P.M 

A.M. 

P.M. 

A.M. 

P.M. 

I 

50 

58 

48 

58 

60 

35 

2 

52 

54 

48 

52 

65 

25 

3 

52 

56 

52 

56 

45 

20 

4 

52 

60 

50 

60 

45 

30 

5 

52 

60 

52 

52 

55 

50 

6 

52 

54 

52 

54 

50 

50 

7 

54 

52 

50 

65 

8 

50 

54 

60 

45 

9 

48 

56 

60 

25 

10 

50 

50 

65 

50 

II 

52 

54 

60 

50 

12 

50 

50 

60 

60 

13 

50 

52 

^5 

50 

14 

50 

54 

60 

50 

48 

54 

70 

50 

16 

50 

50 

70 

60 

Moisture 

It  has  already  been  stated  that  in  curing  sweet  pota- 
toes, moisture  is  given  off.  Part  of  this  moisture  was 
present  in  the  sweet  potato  when  freshly  dug  from  the 
ground;  the  remainder  came  about  from  the  breaking 
up  of  the  starch  into  sugar,  carbon  dioxide  and  water. 

That  moisture  is  given  off  during  sweating  is  a  well- 
known  fact.  However,  the  amount  varies  with  the 
variety,  and  especially  with  the  methods  of  curing.  The 
work  of  Price  (81)  in  Alabama  shows  that  about  24.92 
per  cent  of  moisture  is  lost  during  the  entire  storage 
season.    This  is  shown  in  Table  28. 


The  Curing  Period 


211 


Table  28 
Loss  in  Weight  from  Moisture  Evaporation 


Date 


Weight  in 
Pounds 


Weight 
Lost 


Per  Cent, 
of  Loss 


1915 
November  10. 
November  1 1 . 
November  12. 
November  13. 
November  15. 
November  16. 
November  17. 
November  18. 
November  19. 
November  20. 
November  22 . 
November  23  ■ 
November  24. 
November  25 . 
November  26 . 
November  27. 
November  29 . 
November  30. 
December  i . 
December  2 . 
December  3 . 
December  4. 
December  6. 
December  7 . 
December  8 . 
December  9, 
December  10. 
December  11, 
December  13. 
December  14. 
December  16, 
December  20. 
December  21, 
December  23- 
December  24 
December  25 
December  27 
December  30 

1916 
January  i 
January  14 
February  i 
February  14 
March        13 


120 

118. 2 

117 

116. 1 

II4-5 

113-85 

113-25 

112.86 

112.28 

III. 95 

111.25 

110.74 

110.53 

no. 16 

109 . 82 

109.45 

108.85 

108.65 

108.40 

108.20 

108 

107.70 

107.20 

107 

106.85 

106 . 40 

106.10 

105.80 

105-55 

105 . 10 

104.80 

103.80 

103.30 

103-15 

103 

102.85 

102.35 

102 


1.8 

3 

3-9 

5-5 

6.15 

6.75 

7.14 

7.72 

8.05 

8.75 
9.26 

9.47 
9.84 
10.18 
10.55 
II. 15 
11.35 
11.60 
11.80 
12 

12.30 
12.80 
13 

13-15 
13.60 
13.90 
14.20 

14-45 
14.90 

15-20 

16.20 
16.70 

16.85 

17 

17-15 

17-65 

18 


1-5 

2-5 

3-25 

4-58 

5-12 

5-62 

5-95 

6.43 

6.70 

7.29 

7.71 

7-89 

8.2 

8.48 

8-79 

9-29 

9-45 

9.66 

9-83 
10 

10.23 
10.66 
10.83 
10.96 

11-33 

II. 5 

11-83 

12.04 

12.41 

12.66 

13.5 

13-91 

14.04 

14.16 

14.29 

14.7 

15 


lOI 

19 

15.83 

99 

21 

17.66 

95 

25 

19-83 

93-80 

26.20 

21.83 

90.10 

29.90 

24.92 

212  The  Sweet  Potato 

The  data  in  Table  28  are  not  very  conclusive,  since 
they  are  based  on  only  150  pounds  of  sweet  potatoes, 
stored  in  a  slatted  container.  It  is  doubtful  if  the  same 
amount  of  evaporation  will  occur  in  large  bulks  when 
sweet  potatoes  are  stored  in  bins.  Investigations  by  the 
author  have  shown,  that  on  the  average  in  fairly  well 
constructed  sweet  potato  houses,  the  loss  from  water 
evaporation  during  the  entire  storage  period  varies  6  to 
8  per  cent  in  bins,  and  6  to  15  per  cent  in  hampers  or 
containers.  Similar  results  are  recorded  by  Manns 
(63),  Mooring  (70),  and  others.  One  man  in  Texa? 
with  a  so-called  patent  to  sell,  claims  that  with  his  sys- 
tem of  curing  there  is  practically  no  loss  from  shrinkage 
(moisture  evaporation).  Such  claims  are  unreasonable, 
because  sweet  potatoes,  to  keep  well,  must  lose  6  to  10 
per  cent  in  weight,  but  not  in  bulk. 

Moisture  is  detrimental  to  the  keeping  of  sweet  pota- 
toes. It  is  found,  that  in  houses  where  there  is  the  least 
amount  of  soft  and  black  rot,  the  relative  humidity  does 
not  fluctuate  more  than  50  to  70  per  cent.  However, 
the  greatest  amount  of  loss  from  rots  occurs  in  houses 
where  the  relative  humidity  is  near  saturation  point.  It 
Is  generally  believed  that  infection  can  not  occur  unless 
there  is  an  actual  film  of  moisture  on  the  surface  of  the 
plant  or  roots.  This,  however,  is  not  always  necessary. 
Laurltzen  (61)  has  shown  that  within  certain  limits  of 
humidity  the  spore  is  able  to  absorb  sufficient  water  to 
germinate.  This  is  done  first  by  imbibition  and  later  by 
osmosis.  This  would  seem  to  explain  the  reason  why  it 
is  dangerous  to  allow  the  sweet  potato  house  to  remain 
damp.  Dampness  may  be  gotten  rid  of  by  heat  and  ven- 
tilation. 


The  Curing  Period  213 


Methods  of  Heating  Sweet  Potato  Houses 

The  manager  of  a  potato  house  would  be  greatly  mis- 
led if  he  thinks  that  the  last  word  has  been  said  about 
heating  sweet  potato  houses.  This  is  something  to  be 
worked  out  for  each  individual  house.  While  too  much 
heat  in  poorly  ventilated  houses  is  detrimental,  some 
heat  is  necessary.  In  the  small  house  it  is  obtained 
through  a  sheet  iron,  "air  tight,"  wood  stove.  Coal 
stoves  are  also  satisfactory  although  a  longer  time  is  re- 
guired  to  get  up  heat,  which,  however,  is  maintained 
longer.  When  wood  stoves  are  used  it  is  advisable  to 
start  a  fire  with  dry  wood.  To  maintain  it  a  long  time, 
especially  during  the  night,  a  few  chunks  of  green  wood 
are  put  in.  In  -the  South,  in  the  unit  house  of  5000- 
bushel  capacity,  the  modern  school  house  heating  systeni 
is  recommended.  With  this  system  of  heating,  the  stove 
is  raised  and  placed  over  an  opening  in  the  floor 
through  which  air  enters  from  under  the  house.  The 
air  then  passes  through  a  jacketed  stove  where  it  be- 
comes heated  and  dried  from  contact  with  the  stove. 
By  virtue  of  its  being  lighter,  it  rises  to  the  ceiling  and 
spreads  to  all  parts  of  the  house,  where  it  absorbs 
moisture.  It  then  becomes  heavier  and  settles  on  the 
floor,  where  it  is  sucked  out  and  escapes  through  the 
bottom  openings  of  the  flue.  By  this  method,  a  constant 
strong  circulation  of  warm  dry  air  is  maintained. 

In  the  large  sweet  potato  houses  in  New  Jersey  with 
a  storage  capacity  of  10,000  bushels  or  more,  heat  is 
secured  through  a  hot  air  heater,  or  a  hot  water  boiler 
with  pipes  around  the  walls.  The  heater  in  this  case  is 
located  in  a  cellar,  which  is  utilized  for  storing  canned 
goods,   barrels,  or  even   for  storing  sweet  potatoes. 


214  The  Sweet  Potato 

Medium-sized  potato  houses,  of  25,000-bushel  capacity, 
are  heated  with  good  coal  stoves.  The  location  of  the 
stoves  will  depend  on  the  direction  of  the  cold  winds. 
Frequently  but  one  large  stove  is  used,  when  it  is  placed 
near  the  center  of  the  house.  If  the  cold  wind  strikes 
one  end  of  the  house  it  should  preferably  be  placed  in 
that  end.  Some  houses  have  a  small  stove  at  each  end. 
This  arrangement  is  satisfactory  in  a  long  house.  Still 
others  have  a  stove  in  one  end  with  the  pipe  entering 
the  chimney  in  the  other.  In  very  small  houses  in  the 
South,  heat  is  maintained  through  oil  stoves.  Where 
natural  gas  is  available,  and  this  is  true  for  many  parts 
of  Texas,  heat  is  maintained  by  gas  burners,  placed  in 
the  aisles  of  the  house  or  in  closed  cellars  where  the  heat 
rises  through  a  slatted  bottom  floor.  For  medium-sized 
sweet  potato  houses  in  New  Jersey,  Delaware,  Virginia, 
and  even  in  all  other  states  of  the  South,  a  desirable 
cellar  heating  system  is  recommended  by  Stuckey  (93) 
of  Georgia,  which  is  built  as  follows:  The  walls  of  the 
cellar  from  the  ground  to  the  floor  are  made  as  ifparly 
air-tight  as  possible.  There  are  four  doors  from  the 
cellar,  one  leading  from  the  floor  of  each  bin.  With 
such  an  arrangement  the  heat  may  be  turned  under  one 
or  as  many  bins  as  is  desired.  The  flue  of  the  heater 
extends  to  the  top  of  the  building  through  the  floor  of 
the  hallway  by  means  of  two  elbows.  The  flue  may  con- 
sist of  tiles  or  ordinary  sheet-iron  pipes.  To  furnish 
sufficient  air  for  the  heater,  a  four-inch  tile  pipe  is  put 
in.  This  pipe  extends  from  the  base  of  the  heater, 
through  the  soil,  and  under  the  concrete  foundation 
opening  on  the  outside. 

A  similar  arrangement  can  be  made  where  gas  is 
available.  In  this  case,  a  pit  is  dug  in  the  ground  where 
the  gas  burner  is  installed.    Fresh  air  is  taken  in  from 


The  Curing  Period  215 

a  large  tube  which  extends  outside  (Fig.  4,  bj.  As  the 
gas  burners  are  lighted,  fresh  air  is  drawn  in.  The  air 
as  it  is  heated  rises,  and  can  be  turned  in  to  any  bin  de- 
sired, which  is  regulated  by  means  of  trap  doors. 

The  heating  system  for  the  patent  houses  is  arranged 
somewhat  differently.  This  is  taken  up  on  pages  254 
to  260. 

Thermometers.  Money  spent  for  a  first-class  ther- 
mometer is  money  well  invested.  Many  people  claim 
that  they  can  feel  the  temperature  in  the  potato  house 
and  for  this  reasoi:;i  dispense  with  the  use  of  such  instru- 
ments. This  would  seem  very  improbable,  and  no  suc- 
cessful manager  of  a  potato  house  should  be  without 
thermometers. 

At  least  one  thermometer  should  be  used  for  every 
one  thousand  bushels  of  capacity  and  they  should  be 
well  distributed  through  the  house.  A  lower  ther- 
mometer should  be  hung  on  the  level  with  the  eyes,  and 
an  upper  one  not  higher  than  the  top  of  the  highest  bins. 
The  manager  should  be  careful  not  to  depend  upon  the 
reading  of  one  thermometer  and  accept  that  as  re- 
vealing the  temperature  conditions  of  the  whole  house, 
but  he  should  regularly  make  the  rounds  of  all  the  ther- 
mometers, seeing  to  it  that  the  temperature  gets  neither 
too  high  nor  too  low  in  any  part  of  the  house.  In  case 
the  temperature  above  is  too  high  and  the  temperature 
below  is  correct,  the  ceiling  vents  should  be  opened  at 
once.  In  connection  with  the  Indoor  thermometers  it  Is 
of  course  taken  for  granted  that  one  or  two  will  be  hung 
outside  as  a  guide,  and  for  the  purpose  of  enabling  the 
manager  to  take  advantage  of  outside  weather  condi- 
tions for  ventilation. 


2i6  The  Sweet  Potato 


Ventilation 

It  has  been  previously  stated  that  considerable 
moisture  is  given  off  by  sweet  potatoes  in  storage.  This 
is  especially  true  during  the  curing  season.  This 
moisture  must  not  be  permitted  to  remain  stagnant  in 
the  air.  Elliot  (21)  has  estimated  that  500  bushels  of 
sweet  potatoes  give  off  350  gallons  of  water  during 
storage.  This  must  be  removed  or  driven  out  by  what- 
ever means  possible.  In  the  average  sweet  potato  house, 
provided  with  meagre  facilities  for  ventilation,  this  can- 
not be  accomplished  so  readily.  In  the  unit  5000-bushel 
Texas  A.  and  M.  house,  ventilation  is  provided  by 
means  of  floor  ventilators,  windows,  ceiling  ventilators, 
and  cupolas  (Fig.  22,  a,  b,  d  and  e).  In  the  so-called 
government  houses,  which  are  really  designed  for 
southern  conditions  only,  the  floor  and  ceiling  ventilators, 
as  well  as  cupola,  are  not  provided  for.  Instead,  one  or 
two  small  holes  are  allowed  in  the  aisle  which,  however, 
because  of  their  small  size,  permit  but  very  little  floor 
ventilation.  In  the  large-sized  sweet  potato  houses  in 
New  Jersey,  the  houses  are  too  bulky,  and  of  necessity 
are  built  in  such  a  way  that  the  maximum  amount  of 
ventilation  is  not  always  obtained.  Under  these  con- 
ditions, of  course,  the  installation  of  one  or  two  oscil- 
lating electric  fans  will  be  of  great  benefit.  In  this  way 
the  keeping  of  the  sweet  potatoes  may  be  considerably 
improved  without  necessitating  the  enormous  expense 
of  a  so-called  patent  system.  It  is  sufficiently  clear  from 
the  foregoing  that  the  object  in  ventilation  is  to  rid  the 
storage  house  of  its  excess  moisture. 

Hygrometers.  In  addition  to  thermometers,  it  is  also 
desirable  to  have  one  or  two  hygrometers  indoors,  and 


The  Curing  Period  217 

one  on  the  outside.  The  hygrometer  is  an  instrument 
designed  to  read  the  relative  humidity,  or  water  vapor 
in  the  house.  An  ordinary  Mitthoff  hygrometer  will 
answer  the  purpose.  This  instrument  is  inexpensive, 
and  may  last  two  or  three  years.  It  gives  the  direct 
reading  of  the  relative  moisture  in  the  air.  In  carefully 
watching  the  readings  of  the  outdoor  and  indoor  in- 
struments, the  condition  of  the  humidity  of  the  air  will 
be  known.  Based  on  that  knowledge  the  ventilation  of 
the  house  is  regulated.  At  no  time  should  the  relative 
humidity  of  the  house  be  higher  than  65  to  70  degrees. 
On  the  other  hand,  when  the  hygrometer  registers  a  low 
degree  of  relative  humidity,  it  means  that  conditions 
in  the  house  are  right  for  proper  curing  and  keeping  of 
the  sweet  potatoes. 

Care  After  Curing 

Where  sweet  potatoes  are  destined  for  shipping  to  the 
various  markets,  they  must  of  course  be  cured.  Un- 
cured  or  "green"  sweet  potatoes  will  ship  poorly  if  at 
all.  This  is  the  case  with  banked  potatoes.  It  is  rela- 
tively easy  to  tell  when  the  potato  is  cured  by  merely 
rubbing  its  skin.  When  the  latter  clings  firmly  to  the 
flesh  of  the  potato  it  indicates  that  it  has  been  properly 
cured.  On  the  other  hand  if  the  skin  rubs  off  easily,  the 
potatoes  are  still  green  and  uncured.  Usually  growers 
take  the  sprouting  as  an  indication  of  perfect  curing. 
This  is  generally  true  but  under  these  conditions  it 
might  mean  that  too  much  heat  had  been  used  during 
curing.  It  is  not  harmful  for  potatoes  to  sprout  slightly 
and  this  usually  happens  in  the  average  sweet  potato 
house.  On  the  other  hand  excessively  long  sprouts  in- 
dicate that  the  potato  had  heat  for  too  long  a  period. 


2i8  The  Sweet  Potato 

As  soon  as  the  potatoes  have  been  cured,  the  tempera- 
ture should  gradually  be  lowered  down  to  fifty  degrees 
F.,  and  maintained  there  as  nearly  as  possible.  How- 
ever, it  may  not  always  be  easy  to  maintain  that  low 
temperature,  in  which  case  all  fires  should  be  put  out, 
and  during  the  day  the  doors  and  windows,  but  not  the 
top  ventilator  should  be  closed,  in  order  to  keep  out  the 
often  excessively  warm  or  damp  outdoor  air.  How- 
ever, doors  and  windows  should  be  open  at  night  to  per- 
mit the  cool  air  to  come  in  and  closed  again  in  the  morn- 
ing. 

The  cool  air  will  help  to  maintain  a  low  temperature 
during  the  day.  Should  it  turn  cold  suddenly  it  will 
not,  of  course,  be  necessary  or  safe  to  open  the  doors 
and  windows  at  night,  but  they  may  be  opened  during 
the  day  time  provided  the  outside  temperature  is  not 
below  fifty-five  degrees.  As  a  safe  guide,  therefore, 
whenever  the  outside  temperature  is  not  below  fifty-five 
to  sixty  degrees,  there  need  be  no  fear  of  giving  the 
house  all  the  ventilation  possible  in  order  to  maintain 
low  temperatures  in  dry  weather.  However,  in  wet 
weather,  after  curing,  the  house  should  be  kept  closed, 
except  the  top  ventilators,  and  the  inside  temperatures 
and  relative  humidity  should  be  closely  watched.  As 
long  as  the  humidity  does  not  run  up  above  seventy  de- 
grees and  the  temperature  is  maintained  at  about  fifty- 
five  to  sixty  degrees,  little  needs  to  be  done.  Just  as 
soon  as  the  relative  humidity  rises,  however,  a  little  fire 
should  be  maintained  in  order  to  drive  out  the  excessive 
moisture.  Under  climatic  conditions  of  New  Jersey  or 
Delaware,  for  instance,  there  will  be  no  difficulty  in 
maintaining  a  low  temperature  of  forty-five  to  fifty  de- 
grees after  curing.  In  this  case  the  fire  is  merely  lowered 
and  the  thermometer  closely  watched.  If  the  outside  air 


The  Curing  Period  219 

is  below  45  degrees  F.  all  the  windows  should  be  closed 
except  the  ceiling  ventilators.  Enough  fire  should  be 
maintained  to  hold  the  indoor  temperature  to  about  50 
degrees  F.  If  the  weather  is  mild  and  the  outside  air 
about  60  degrees,  the  house  may  be  given  all  the  ven- 
tilation possible  and  the  fires  reduced.  At  night,  how- 
ever, the  doors  and  windows  should  be  closed  and  if  it 
turns  too  cold  even  the  ceiling  ventilators  should  be  shut, 
and  enough  fire  maintained  to  keep  the  temperature 
about  50  to  55  degrees  F. 

Critical  Periods  During  Storage 

Most  growers  agree  that  the  critical  period  which  the 
sweet  potatoes  undergo  in  storage  is  the  time  of  sweat- 
ing. This  is  true  since  at  that  time  there  is  given  off  an 
excess  of  moisture  from  the  roots,  which  accumulates 
in  the  house,  imless  ventilation  is  good.  It  is  this 
moisture  that  is  conducive  to  rots  and  this  condition 
constitutes  the  critical  period.  However,  sweet  potatoes 
in  storage  undergo  more  than  one  critical  period.  It  is 
a  mistake  to  think  that  the  roots  sweat  but  once.  There 
is  moisture  given  off  practically  every  day  while  in 
storage,  although  less  in  amount  than  when  the  potatoes 
are  sweating.  Nevertheless,  little  as  it  is,  if  that  moist- 
ure is  not  carried  away,  it  will  accumulate  and  cause 
damage.  In  poorly  constructed  and  ventilated  houses, 
the  sweet  potatoes  are  in  a  critical  period  throughout 
the  time  of  storage.  Other  critical  periods  which  are 
the  most  difficult  to  bridge  over  in  the  South,  are  the 
warm,  moist,  and  muggy  days  of  January  and  Febru- 
ary. Here  in  occasional  seasons,  the  weather  suddenly 
turns  very  warm  and  the  air  humid.  During  such 
times,  natural  ventilation  is  ineffective,  in  which  case 


220  The  Sweet  Potato 

artificial  ventilation  is  resorted  to,  one  or  more  oscil- 
lating fans  being  used  as  indicated  on  p.  216. 

Many  growers  commit  the  error  of  shifting  their  po- 
tatoes after  they  have  been  put  in  the  bins  and  cured. 
This  is  generally  done  when  an  excessive  amount  of 
rots  is  noticed.  While  this  practice  may  be  excused  on 
the  ground  that  it  is  necessary  to  save  the  sound  ones 
by  removing  the  rotted  ones,  it  is  not  a  good  policy  to 
move  the  potatoes  after  they  have  been  put  in  the  bins, 
irrespective  of  the  rotting,  because  such  a  condition 
could  naturally  be  traced  to  a  poor  house  or  to  poor 
management.  If  this  policy  is  continued,  the  moving  of 
the  potatoes  from  one  place  to  another  will  result  in 
heavy  losses  from  rot.  When  considerable  soft  rot  is 
noticed  in  the  house,  the  first  thing  to  do  is  to  provide 
all  the  ventilation  possible.  By  careful  manipulation  of 
the  heating  and  the  opening  and  closing  of  ventilators, 
the  relative  humidity  could  be  brought  down  to  60  or  70 
degrees  F.  If  it  is  found  impossible  to  remedy  the  faulty 
heating,  or  ventilation,  or  if  the  house  is  too  cold,  and 
the  heat  cannot  be  maintained,  the  potatoes  had  better 
be  sold  immediately. 


CHAPTER  XVII 

STORAGE  HOUSE  CONSIDERATIONS 

Nearly  every  one  who  has  proper  soil  conditions,  and 
reasonable  climate  may  produce  a  crop  of  sweet  pota- 
toes. The  largest  profits  are  made  when  the  crop  is 
properly  cured  and  housed  over  winter  in  correctly  con- 
structed houses  (Kiln  drying  houses).  However,  many 
fail  to  provide  the  right  curing  conditions.  The  low 
margin  of  profit  from  stored  sweet  potatoes  is  not  al- 
ways due  to  low  market  prices,  but  rather  to  losses  from 
rots  which  are  favored  by  various  factors. 

The  Growing  Season.  Careful  observations  and 
studies  have  shown  that  the  growing  season  in  the  field 
plays  a  very  important  role  in  determining  the  keeping 
of  the  crop  in  storage.  Generally  speaking,  during 
wafm,  moist  summer  seasons,  the  growth  of  sweet  pota- 
toes is  such  as  to  be  conducive  to  poor  keeping.  Under 
these  conditions,  the  roots  are  watery  when  harvested; 
hence  the  great  difficulty  in  properly  curing  them  later, 
especially  if  the  weather  is  wet  and  warm  during  the 
sweating  period.  On  the  other  hand,  long  droughts 
during  the  growing  seasons  accompanied  by  a  continued 
wet  spell  before  harvesting  is  also  detrimental.  Under 
these  conditions,  the  roots  grow  and  develop  very 
slowly  at  first,  more  rapid  but  uneven  growth  sets  in 
later  and  this  means  soft,  watery  and  cracked  potatoes, 
which  are  hard  to  cure,  and  of  poor  keeping  quality. 
The  most  favorable  season  is  one  in  which  the  rainfall  is 


222  The  Sweet  Potato 

somewhat  below  the  average,  falHng  regularly  at  the 
beginning  of  the  season,  and  decreasing  at  harvesting. 

Preparing  the  House  for  Storage 

Some  time  before  harvesting,  and  in  any  slack  time 
during  the  summer,  if  possible,  the  house  should  be 
carefully  overhauled  and  necessary  repairs  made. 
Broken  windows  should  be  replaced  and  careful  ex- 
amination made  to  see  that  the  doors,  ventilators  and 
ceiling  and  floor  vents,  fit  well,  that  the  roof  and  floor 
are  tight,  and  that  all  rat-holes  are  closed.  Bins  which 
need  repair  should  also  receive  equal  attention.  The 
stove  and  chimney  should  be  overhauled  and  cleaned. 

In  dealing  with  a  house  where  sweet  potatoes  have 
been  stored  before,  it  would,  of  course,  be  folly,  and  at 
least  unsanitary,  to  bring  the  new  crop  in  without  first 
giving  it  a  thorough  cleaning.  By  utilizing  all  spare 
time  in  the  summer,  the  alert  grower  will  make  it  a 
point  to  give  his  house  a  thorough  cleaning  and  remove 
all  rotted  potatoes  and  dust  which  came  in  as  adhering 
dirt  with  the  previous  crop.  These  left-over,  mummied 
potatoes  and  the  dust  are  usually  loaded  with  various 
germs,  which  produce  diseases  in  the  sweet  potato.  This 
refuse  should  be  carefully  removed,  and  all  indoor  wood 
work  should  be  disinfected  by  spraying  with  a  solution 
of  concentrated  lime  sulphur  at  the  rate  of  one  gallon  of 
the  stock  solution  to  nine  gallons  of  water  or  blue  stone 
dissolved  at  the  rate  of  five  pounds  in  fifty  gallons  of 
water.  An  ordinary  bucket  pump,  with  a  long  nozzle, 
may  be  used  to  apply  the  disinfectant.  With  blue  stone 
(copper  sulphate)  only  wooden  vessels  should  be  used, 
as  metal  ware  will  be  corroded  by  the  chemical.  The 
copper  sulphate  may  be  dissolved  more  readily  by  sus- 


Storage  House  Considerations    223 

pending  it  over  night  in  water  in  a  muslin  sack.  The 
advantage  of  copper  sulphate  over  lime  sulphur  is  its 
freedom  from  any  disagreeable  odor.  Both  however 
are  poisonous  and  great  care  should  be  taken  to  prevent 
any  of  the  farm  animals  or  children  from  drinking  them. 
No  injury  whatsoever  occurs,  when  the  poison  is  acci- 
dentally applied  to  the  hands  or  clothing.  When  lime 
sulphur  is  used  it  also  acts  as  an  insecticide,  killing  any 
possible  insect,  or  insect  eggs  which  may  hide  or  cling 
to  the  wood  work.  Another  reliable  method  for  dis- 
infecting sweet  potato  houses  is  the  formaldehyde  gas 
method,  used  as  follows :  The  house  is  at  first  made  as 
tight  as  possible  by  closing  all  doors,  windows,  and 
ventilators  except  the  exit  door.  Each  one  thousand 
cubic  feet  of  house  space  will  require  three  pints  of 
forty  per  cent  formaldehyde  and  twenty-three  ounces  of 
potassium  permanganate.  To  carry  out  this  operation  it 
is  essential  to  use  a  crock  of  three  gallons'  capacity  for 
every  thousand  bushels  house  space.  Where  deep  ves- 
sels are  not  used  the  chemical  action  will  be  so  violent 
that  it  will  boil  over,  and  the  effect  of  the  potassium  per- 
manganate will  be  lost  to  a  certain  extent.  The  formal- 
dehyde and  the  potassium  permanganate  should  be 
divided  equally  into  as  many  portions  as  there  are 
crocks.  The  permanganate  is  placed  in  the  crocks  first 
and  the  formaldehyde  poured  on  it,  after  which  the 
operator  leaves  the  house  at  once,  closing  the  door 
tightly  behind  him.  The  operator  should  pour  the  for- 
maldehyde into  the  crock  farthest  from  the  door,  first, 
working  backwards  toward  the  exit  door.  This  will 
obviate  inhaling  the  formaldehyde  fumes,  which  are 
poisonous.  For  best  results  it  is  necessary  to  sprinkle 
water  on  the  floor  of  the  sweet  potato  house  before 
fumigating  with  formaldehyde  and  potassium  perman- 


224  The  Sweet  Potato 

ganate.  The  added  moisture  in  this  case  will  insure  a 
better  chemical  reaction.  It  is  also  necessary  for  safety 
that  the  operation  be  performed  by  two  persons,  so  that 
in  case  of  accident  the  other  will  be  on  hand.  Under  the 
present  abnormal  prices  both  the  formaldehyde  and  the 
potassium  permanganate  are  too  high  to  justify  their 
use.  Under  normal  prices,  however,  this  method  is  very 
desirable,  as  it  kills  the  spores  of  disease-producing  or- 
ganisms as  well  as  rats  which  may  be  infesting  the 
house.  Moreover,  this  method  is  a  great  labor-saver. 
Many  growers  often  burn  sulphur,  believing  that  this 
acts  as  a  disinfectant.  Investigations,  however,  ha\^e 
not  shown  this  to  be  a  fact,  although  burning  the  sul- 
phur is  none  the  less  effective  in  controlling  mites  and 
also  in  killing  rats.  In  disinfecting  with  formaldehyde 
the  house  should  be  kept  closed  for  at  least  forty-eight 
hours  or  longer  if  desired,  after  which  time  it  should  be 
opened  and  allowed  to  air.  One  of  the  doors  should 
be  opened  at  first.  In  six  to  twelve  hours  most  of  the 
formaldehyde  fumes  will  have  escaped,  when  the  re- 
mainder of  the  doors  and  windows  as  well  as  the  ven- 
tilators should  be  opened. 

After  the  house  has  been  cleaned  and  disinfected,  and 
about  two  days  before  the  crop  is  to  be  brought  from 
the  field,  it  is  desirable  to  make  a  little  fire,  in  order  to 
dry  the  house  and  to  raise  the  temperature  to  70  degrees 
F.    At  this  point  the  house  is  ready  for  storing. 

Filling  the  House 

It  is  the  customary  belief  of  managers  of  sweet  potato 
houses  that  it  is  necessary  to  fill  the  house  just  as  rapidly 
as  possible,  fill  each  bin  at  a  time,  and  one  after  the 
other.    The  reason  given  is  that  the  potatoes  should  be 


Storage  House  Considerations    225 

put  in  the  bins  so  that  they  may  be  cured  as  nearly  at 
the  same  time  as  possible.  This,  however,  is  not  always 
necessary,  and  in  fact  not  desirable,  especially  during 
damp  weather,  when  the  potatoes  come  in  wet  or  when 
dug  late  in  the  season  during  rainy  weather.  In  this 
case,  the  bins  will  be  filled  full  at  one  time,  and  one  after 
the  other,  and  the  sweet  potatoes  will  be  given  little  op- 
portunity to  dry  on  the  outside.  As  a  result,  they  will 
soft-rot  badly.  A  bin  should  never  be  entirely  filled  at 
one  time.  To  secure  good  keeping,  the  sweet  potatoes 
as  they  come  from  the  field  should  be  spread  out  in 
small  quantities  in  as  many  bins  as  possible.  This  will 
give  them  a  chance  to  dry  and  prevent  their  going 
through  a  heating  process.  The  following  plan  of  filling 
a  potato  house  will  tend  to  encourage  more  thorough 
curing.  This  applies  to  storage  houses  with  bins,  al- 
though a  similar  system  may  also  be  used  when  potatoes 
are  stored  in  hampers  or  crates.  Figure  23,  a,  repre- 
sents a  cross-section  through  the  bins  of  a  storage  house. 
A  and  B  represent  the  inner  back  bins;  C  and  D  the 
front  bins.  When  the  sweet  potatoes  are  brought  in, 
they  are  first  placed  in  all  the  bins  marked  A,  the  bins 
B  being  left  vacant.  This  gives  the  potatoes  in  bins  A 
a  good  chance  to  dry  and  cool  down  to  the  temperature 
of  the  storage  house.  When  this  is  done  the  potatoes 
are  put  in  all  the  bins  marked  B.  With  this  method,  all 
the  front  bins  C  and  D  are  still  empty  and  permit  the 
bulks  in  bins  A  and  B  favorable  opportunities  to  dry. 
When  all  the  inner  bins  A  and  B  are  filled,  all  the  bins 
marked  C  are  then  filled  with  potatoes,  bins  D  being 
left  vacant  to  be  filled  last.  This  method  encourages 
even  drying  and  prepares  all  the  potatoes  for  more  uni- 
form curing.  With  this  system,  a  little  fire  should  be 
kept  in  the  house  until  the  house  is  entirely  full ;  there- 


226  The  Sweet  Potato 

after  curing  may  be  started.  By  following  the  above 
method  of  filling  the  storage  house  and  taking  advan- 
tage of  all  the  natural  means  of  ventilation,  the  curing 
period  may  be  reduced  considerably,  and  the  potatoes 
cured  with  a  moderate  amount  of  heat.  Another  pre- 
caution which  is  generally  overlooked  is  that  of  storing 
different  varieties  in  the  same  house.  This  is  unwise, 
since  different  varieties  require  specific  handling.  The 
"Gold  Skin,"  for  instance,  of  New  Jersey  and  Delaware 
is  considered  a  wet  potato,  containing  less  starch  and 
more  sugar  and  water.  Such  a  variety,  therefore,  needs 
more  curing  to  rid  it  of  its  excessive  moisture.  When 
stored  with  a  dry  potato  such  as  the  "Big  Leaf,"  which 
requires  less  curing.  Gold  Skins  could  not  be  dried  prop- 
erly in  large  bulk.  Such  a  variety  would  keep  much 
better  if  stored  in  a  separate  house.  This  is  of  special 
importance  to  large  commercial  houses  where  various 
varieties  are  often  handled  In  the  same  house.  In  small 
houses  the  curing  of  varieties  separately  can  not  always 
be  done. 

Another  precaution  in  filling  the  storage  house  is  to 
place  all  the  potatoes  from  the  same  field  in  bins  by 
themselves.  In  large  houses  where  sweet  potatoes  are 
brought  in  by  different  growers,  all  the  roots  from  the 
same  man  should  be  stored  together  in  a  separate  place. 
It  should  be  remembered  that  all  the  growers  do  not  give 
their  potatoes  an  equal  amount  of  care.  By  mixing  the 
roots  from  various  fields  and  individuals,  one  takes  the 
risk  of  spreading  disease  through  the  entire  bulk. 

Storing  in  Bins  Versus  Containers 

In  New  Jersey  the  sweet  potatoes  in  the  house  are 
stored  in  bushel  hampers  or  in  crates  instead  of  bins. 


Storage  House  Considerations    227 

This  method  is  satisfactory  only  in  large  commercial 
houses  with  a  capacity  of  eighty  to  one  hundred  thou- 
sand baskets.  Crates  or  hampers  in  this  case  no  doubt 
facilitate  the  drying  or  curing.  In  small-sized  houses 
with  capacities  that  range  from  a  few  hundred  bushels 
to  two  thousand  bushels  the  storing  in  crates  or  hampers 
is  objectionable  because,  under  these  conditions,  the 
roots  are  subject  to  greater  drying  and  shrinkage.  Even 
in  the  largest  commercial  houses,  bins  could  be  used  to 
advantage,  provided  they  are  divided  into  small  4^X5' 
compartments  with  the  necessary  air  space  between  the 
bins  (Fig.  22,  c).  The  tendency  in  the  larger  houses  in 
the  South  is  to  store  altogether  in  containers.  With  this 
method,  the  cost  of  bin  construction  is  eliminated  en- 
tirely. Moreover,  after  the  storage  season,  the  house 
remains  free  and  unobstructed,  and  may  be  utilized  for 
storing  Irish  potatoes,  peanuts,  hampers,  etc.  Many 
growers  store  in  the  same  containers  which  are  used  for 
shipping  the  crop.  Since  sweet  potatoes  must  be  re- 
packed and  graded  for  shipping,  the  above  method  is 
economical  as  it  requires  no  extra  expense  of  money  for 
storage  receptacles.  Many  growers  store  in  bushel 
peach  baskets,  others  in  hampers,  others  in  bushel  boxes 
or  crates  especially  built  for  that  purpose.  When  con- 
tainers are  used  for  storage,  a  platform  consisting  of  a 
raised  false  floor  is  made  to  provide  the  necessary  ven- 
tilation, just  as  was  done  in  the  case  of  bins. 


CHAPTER  XVIII 

CONSTRUCTION    OF  COMMERCIAL   CURING   HOUSES 

Before  considering  the  various  types  of  storage 
houses  used,  it  will  not  be  out  of  place  to  consider  their 
evolutionary  development.  In  the  tropics,  the  sweet 
potato  is  practically  a  perennial.  There,  the  roots  are 
dug  a  few  at  a  time,  and  only  as  needed  for  eating  pur- 
poses. In  the  sub-tropical  countries  and  where  frosts 
are  sufficient  to  kill  vegetation,  the  sweet  potato  must 
be  harvested.  In  the  first  attempt  at  storing  this  crop 
the  banking  method  was  employed.  As  unsatisfactory 
as  this  method  is,  it  answered  the  purpose.  However, 
when  sweet  potatoes  were  recognized  as  a  commercial 
crop  and  the  acreage  extended,  better  storage  methods 
had  to  be  developed.  Unfortunately  little  is  known  as 
to  how  this  evolution  from  storing  sweet  potatoes  in 
banks  to  storing  in  regular  storage  houses  came  about. 

Mr.  W.  B.  Gordy  of  Laurel,  Delaware,  claims  that 
his  grandfather  was  the  first  to  build  a  sweet  potato 
house  in  1849.  An  ordinary  pit  was  dug  under  the 
kitchen  stove,  deep  enough  to  contain  about  ten  bushels 
of  sweet  potatoes.  The  heat  from  the  stove  helped  to 
cure  the  potatoes.  When  this  was  done,  they  were  cov- 
ered with  sand,  and  used  when  desired.  A  few  years 
later  Mr.  Gordy' s  grandfather  decided  to  place  his  pota- 
toes in  a  small  log  cabin  which  was  heated  by  a  wood 
stove.  There  are  other  old  growers  still  living,  in  New 
Jersey  and  in  Maryland,  each  of  whom  claims  to  have 
originated  the  storage  house  idea. 
228 


Commercial  Curing  Houses      229 

An  undated  pamphlet,  "Keeping  Sweet  Potatoes,"  by 
J.  W.  Beeson,  President  of  Meridian  College,  Meridian, 
Miss.,  has  this  statement:  "The  Meridian  College  of 
Meridian,  Mississippi,  has  been  making  experiments  for 
many  years  in  order  to  discover  a  plan  by  which  sweet 
potatoes  can  be  kept  with  reasonable  certainty  to  be 
marketed  when  prices  are  higher.  We  now  have  solved 
this  problem."  Mr.  Beeson  further  states:  "The  United 
States  Department  of  Agriculture  at  Washington,  D.  C, 
sent  a  man  to  study  our  plan,  pronounced  it  a  success, 
and  got  out  a  bulletin  on  the  subject  but  forgot  to  give 
the  College  credit  for  the  invention.  We  discovered  the 
plan  and  built  the  first  house  ever  built."  Mr.  Beeson's 
storage  house  is  not  different  from  the  small  house  or- 
dinarily built  in  the  South.  Neither  is  it  certain  that  he 
"built  the  first  house  ever  built."  It  is  more  likely  that 
the  sweet  potato  storage  house  idea  originated  in  New 
Jersey  or  Delaware,  where  sweet  potatoes  naturally  need 
more  protection  during  the  winter.  From  the  above 
two  states  the  storing  of  sweet  potatoes  in  especially 
constructed  houses  has  gained  in  favor  wherever  this 
crop  is  grown  in  the  United  States. 

Progress  in  the  development  and  improvement  of  the 
sweet  potato  storage  house  is  based  on  knowledge  of 
the  culture  and  diseases  of  the  sweet  potato.  Much  is 
still  to  be  learned  about  this  apparently  perplexing  crop. 
The  ideal  sweet  potato  house  does  not  exist  as  yet; 
neither  has  the  last  word  been  said  about  it. 

Type  of  House 

The  sweet  potato  houses  most  commonly  constructed 
are  frame  structures  (Fig.  24,  c  and  d).  These  are 
relatively  inexpensive  and  easy  to  build.     Houses  are 


230  The  Sweet  Potato 

frequently  built  of  concrete;  these,  however,  have  not 
as  yet  proved  their  worth,  since  it  is  difficult  to  prevent 
moisture  from  collecting  on  the  walls.  This  may,  to 
a  large  extent,  be  overcome  by  lining  the  inner  walls 
with  lumber.  Sweet  potato  storage  houses  are  often 
also  built  of  bricks  (Fig.  24,  a  and  b).  To  be  satis- 
factory, the  walls  should  be  built  of  a  double  layer  of 
bricks,  with  a  small  dead  air  space  between.  Storage 
houses  are  now  being  built  of  hollow  tile. 

Foundation.  The  foundation  may  be  in  the  form  of 
pillars  for  raised  frame  house  or  of  solid  walls  for 
houses  built  with  cellars.  The  raised  frame  structures, 
girders  6  by  10,  or  8  by  8  inches  are  placed  on  the  pil- 
lars. The  foundation  itself  is  often  built  of  stone,  ce- 
ment, or  bricks.  In  any  case,  it  should  extend  about  20 
inches  above  ground  level.  Plates  2  to  3  inches  thick, 
and  8  to  10  inches  wide  are  placed  on  the  wall.  In  New 
Jersey,  Delaware,  Maryland,  and  Virginia,  foundation 
walls  are  used  principally  rather  than  pillars.  In  this 
case  small  windows  should  be  placed  in  the  foundation 
wall  to  provide  means  of  intake  of  outdoor  air  for  the 
cellar  or  heating  room.  Whether  pillars  or  solid  out- 
side foundation  walls  are  used,  center  pillar  supports 
should  not  be  overlooked. 

Walls.  The  principles  of  building  various-sized  stor- 
age houses  are  about  the  same.  The  walls  of  the  storage 
house  according  to  Thomson  (106),  are  made  by  setting 
2-by-4-inch  studs  on  the  girders  every  2  feet  and 
nailing  them  to  the  sleepers.  On  the  outside  of  the  studs 
i-by-6-inch  boards  are  nailed  diagonally  to  brace  the 
wall;  over  these  a  layer  of  heavy  building  paper  is 
tacked,  and  matched  siding  then  put  on.  A  layer  of 
l-by-6-inch  boards  is  nailed  on  the  inside  of  the  stud- 
ding, then  a  layer  of  building   paper,   and   over   this 


Commercial  Curing  Houses      231 

matched  boards.  In  the  lower  South,  the  first  layer  of 
boards  on  the  inside  of  the  studding  may  be  omitted  so 
far  as  the  control  of  temperature  is  concerned,  but  in 
regions  of  high  humidity  (near  the  seacoast)  it  is 
deemed  advisable  to  use  four  layers  of  boards,  two  on 
the  inside  and  two  on  the  outside  of  the  frame,  as  sug- 
gested above.  The  tighter  the  walls,  the  less  difficulty 
will  be  encountered  in  controlling  both  temperature  and 
moisture.  Two  2-by-4-inch  pieces  should  be  placed  on 
top  of  the  studding  for  "double  plates,"  to  which  the 
rafters  are  nailed.  The  floor  is  made  by  laying  i-by-6- 
inch  sheathing  over  the  joists,  then  a  layer  of  heavy 
building  paper,  and  over  this  i-by-4-inch  tongue-and- 
groove  flooring.  The  building  may  be  covered  with 
shingles,  roofing  paper,  galvanized  iron,  or  any  other 
kind  of  roofing  material;  but  galvanized  iron  is  to  be 
preferred,  because  it  is  durable  and  lessens  danger  from 
fire,  thus  reducing  the  rate  of  insurance.  2-by-2-inch 
scantlings  are  used  for  rafters,  and  the  roof  made  tight 
to  keep  out  the  cold.  The  rafters  should  be  cut  to  fit 
over  the  plate  at  the  lower  end  and  to  fit  snugly  against 
the  ridge  pole  at  the  upper  end.  On  the  outside  of  the 
rafters  a  layer  of  i-by-6-inch  sheeting  is  placed,  then 
a  layer  of  building  paper,  then  another  layer  of  i-by-6- 
inch  sheeting,  and  over  this  the  roofing  material.  On 
the  inside  of  the  rafters  a  layer  of  i-by-6-inch  sheeting 
is  nailed,  then  a  layer  of  heavy  building  paper,  and  over 
this  a  layer  of  tongue-and-groove  ceiling.  If  desired, 
joists  may  be  placed  across  the  building  on  top  of  the 
eave  plates,  and  the  sheeting,  paper,  and  tongue-and- 
groove  material  nailed  to  the  top  side  of  them  instead 
of  to  the  rafters.  These  joists,  if  securely  nailed  to 
the  plate,  will  serve  for  tying  the  sides  of  the  building, 
together,  as  well  as  for  carrying  the  insulated  ceiling. 


232  The  Sweet  Potato 

In  a  large  house,  this  method  of  celling  is  very  satis- 
factory, as  it  gives  loft  space  above  the  storage  room 
and  requires  less  ceiling  material. 

The  sides  of  the  building  should  be  tied  together,  to 
prevent  spreading.  This  can  be  done  by  nailing  2-by-4- 
inch  pieces  to  the  plates  or  to  the  lower  ends  of  the 
rafters.  It  would  be  an  advantage  to  have  these  pieces 
over  the  bin  supports. 

The  space  between  the  walls  should  be  left  open,  be- 
cause any  material  used  to  keep  out  the  cold  will  absorb 
moisture.  Many  storage  houses  have  been  built  with 
sawdust,  shavings,  or  similar  material  between  the 
walls,  but  this  practice  should  never  be  followed.  Saw- 
dust will  take  up  moisture  and  when  once  wet  will  dry 
out  with  difficulty.  This  moisture  will  keep  the  house 
damp  and  cause  the  walls  to  rot.  The  air  space  is  a  good 
insulator  if  the  walls  are  made  tight. 

Aisle  Space.  The  average  sweet  potato  house  does 
not  have  sufficient  aisle  space.  Ordinarily,  but  one  cen- 
tral aisle  is  allowed,  whereas  the  bins  on  each  side  are 
placed  against  the  walls  or  a  few  inches  from  it.  Bins 
should  never  be  permitted  to  be  placed  close  to  the  wall. 
Sufficient  aisle  space  should  be  allowed  between  the 
bins  and  the  wall  (Fig.  22,  d  and  e). 

Ventilators.  The  secret  of  a  good  house  is  its  facili- 
ties for  ventilation.  This  is  made  possible  through  trap 
door  floor  ventilators  in  all  the  aisles  (Fig.  22,  d  and 
e).  Ventilation  can  also  be  added  through  numerous 
doors  and  windows  (Fig.  22,  a).  The  bottom  of  the  win- 
dows should  be  within  18  inches  or  2  feet  of  the  floor. 
Both  doors  and  windows  must  be  made  to  close  tightly 
so  as  to  keep  out  the  cold  wind  whenever  necessary.  All 
windows  should  be  made  to  open  from  the  inside.  This 
is  possible  only  when  sufficient  aisle  space  separates  the 


Commercial  Curing  Houses      233 

bins  from  the  walls.  In  addition,  shutters  built  inside 
of  the  windows  will  help  to  keep  out  cold  air.  The  bot- 
tom of  the  floor  ventilators  should  be  covered  with 
^-inch  galvanized  wire  cloth  to  keep  out  rats  and  mice. 

Cupola.  The  cupola  (Figs.  22,  a,  25,  a  and  b)  solves 
the  roof  ventilation.  The  opening  into  the  cupola  is 
controlled  by  means  of  trap  doors  in  the  interior  of  the 
house  ceiling. 

Bins.  The  bins  are  divided  into  four  quarters 
(Fig.  22,  c)  consisting  of  two  lower  and  two  upper. 
This  division  into  small  compartments  reduces  the  bulk 
of  potatoes  in  each  portion,  to  facilitate  the  curing.  The 
bins  are  raised  above  the  floor  so  as  to  allow  circulation 
of  air  from  underneath. 

Where  it  is  not  desired  to  store  in  bins,  the  same 
house  may  be  utilized  for  storing  in  hampers,  baskets,  or 
crates.  For  this  purpose  slatted  platforms,  covering  the 
same  floor  space  as  the  bins,  may  be  built,  upon  which 
the  containers  are  placed. 

Loading  Platform.  In  connection  with  the  outside  of 
the  house,  there  is  a  loading  platform  (Fig.  23,  c).  This 
is  built  to  facilitate  the  unloading  of  the  potatoes  from 
the  wagon  into  the  house,  or  in  taking  the  potatoes  from 
the  house  for  shipment. 


CHAPTER   XIX 

ESTIMATE  REQUIREMENTS  OF  STORAGE  HOUSES 

The  kind  and  the  capacity  of  the  house  would 
naturally  depend  on  the  acreage.  No  one  should  under- 
take to  build  a  large  house  if  he  has  only  a  small  amount 
of  sweet  potatoes  to  store.  Under  these  conditions  it 
would  be  difficult  to  keep  the  house  without  wasting  fuel 
or  chilling  the  potatoes.  On  the  other  hand  it  is  a  mis- 
take to  build  a  small  house  to  take  care  of  a  large  acre- 
age, as  in  this  case  the  house  will  naturally  be  filled  to 
overflowing  and  make  it  impossible  to  take  care  of  the 
ventilation  which  is  so  essential.  Progressive  growers, 
therefore,  first  of  all  decide  on  their  acreage  and  build 
the  size  of  house  accordingly. 

On  the  farm,  whether  the  house  is  large  or  small,  it 
should  be  located  not  far  from  the  home.  In  this  way 
it  will  be  possible  to  give  it  all  the  necessary  care.  The 
very  large  commercial  house  should  be  located  near  a 
railroad  switch.  This  will  do  away  with  much  un- 
necessary hauling,  which  never  benefits,  but,  on  the  con- 
trary, injures  the  sweet  potatoes. 

The  Small  House 

By  a  small  house  is  here  meant  one  with  a  capacity  of 
500  bushels.     The  small  house  in  New  Jersey,  Dela- 
ware,   Maryland,    or   Virginia,    is    usually    built    two 
stories  high,  and  the  foundation  wall  built  deep  in  the 
234 


Requirements  of  Storage  Houses   1235 

ground.  In  the  South,  the  small  house  consists  of  but 
one  story,  and  the  floor  is  raised  from  the  ground  on 
pillars,  in  order  to  permit  ventilation  from  underneath. 
For  the  South,  the  small  house  recommended  is  the 
small  "government"  house  of  500-bushel  capacity.  It 
could  be  decidedly  improved  by  modeling  it  after  the 
Texas  A.  and  M.  house  (Fig.  22,  a  to  f). 


Bill  of  Materials  for  a  500-BusHEL  House  * 

DIMENSIONS,  I2'o"Xl6'o".      CAPACITY,  5OO  BUSHELS 

Quantities  are  for  dimensions  shown  on  drawing  and 
must  be  altered  if  dimensions  are  changed.  Footings 
should  be  carried  below  frost  line  or  to  solid  ground. 

Concrete 

Mixture — One  (i)  part  Portland  cement,  three  (3) 
parts  sand,  and  five  (5)  parts  gravel  or  broken 
stone;  or  one  (i)  part  Portland  cement  and  six 
(6)  parts  bank  run  gravel 

Quantities  for  Concrete — Cement,  6  sacks ;  sand,  20 
cu.  ft. ;  gravel,  3 1  cu.  ft. ;  or  cement,  6  sacks ;  bank 
run  gravel,  1.5  cu.  yds. 
f 

Chimney 

190  brick 

Mixture  for  Mortar — One  (i)  part  Portland  ce- 
ment, three  (3)  parts  sand 
Cement,  i  sack ;  sand,  4  cu.  ft. 
1-6"  T.  C.  thimble 
6  linear  ft.  of  8"X8"  T.  C.  flue  lining    , 

*  Furnished  by  the  office  of  Public  Roads,  and  Rural  Engineering, 
United  States  Department  of  Agriculture. 


236  [The  Sweet  Potato 

Lumber 

Girders 

2-6"Xio"Xi2'o" 

3-6"Xio"Xi6'o" 
Joists 

i7-2"X8"Xi2'o" 
Studs 

i9-2"X4"Xi6'o" 
Plates 

6-2"X4"Xi6'o" 

6-2"X4"Xi2'o" 
Ties 

4-2"X4"Xi2'o" 
Rafters 

ii-2"X4"Xi6'o" 

i-i;X6"Xi8'  o"  (ridge) 
Sheeting 

2,084  B.  M.  i"X6"  (includes  20  per  cent  waste) 
Flooring 

1,000  B.  M.  i"X4"  T.  &  G.  flooring  (includes  25 

per  cent  waste) 
Drop  siding 

615  B.  M.  i"X6"  (includes  20  per  cent  waste) 
Platform 

3-2"X4"Xi2'o" 

i-2"X8"Xi4'o" 

3-2"X8"Xi2'o" 

i-4"X4"X6'o" 

I-2"Xl2"Xl2'0" 

2-i"Xio"Xi4'o" 
Paper 

40  squares' 
Trim 

4-i>^"X4>4"Xi8'o"  S.  4  S 

4-i^"X4>^"Xi4'o"  S.  48 

2-i"X6"Xi6'o"  S.  4S 


Requirements  of  Storage  Houses    237 

2-i"X8"Xi6'o"  S.  4S 

2-i"X8"Xi2'o"  S.  4S 

2-i"X6"Xi8'o" 

70  Lin.  ft.  ij4"X2'^"  drip  moulding 
Vent  in  roof 

i-i"Xi2"Xi4'o"  S.  4S 
Bins 

6-2"  X4"X  16^0" 

3-2"X4"Xi2'o" 

2-2"X2"Xi6'o" 

6-i"X2"Xi6'o" 

34-i"X4"Xi2'o" 

65-i"X4"Xi4'o" 
Chimney 

i-2"X6"Xi2'o"  (platform) 
Roof  covering  as  desired,  for  290  square  feet 

Miscellaneous 

2  double  hung  sash  and  frames,  for  12  lights  9"Xi2" 
glass 

I  No.  2  glazed  door  3'  o"X7'  o",  6  lights  8"Xio" 

glass 
I  frame  for  glazed  door  3'  o"X7 

3  pair  6"  galv.  T  hinges 

I  pair  2j^"X2}^"  galv.  hinges 

1  pair  3>^"X3>4"  loose  pin  butts  for  glazed  door 
1-2"  cleat 

1-2"  window  pulley 
12  feet  oi  y^"  rope 
4ys"Xf  bolts  with  4"  rings 
9^"X24"  bolts,  nuts,  and  washers 

4  sq.  ft.  y  mesh  wire  cloth 

2  J4"X2>^"  w.  steel  straps 
4  M"X3"  lag  screws 

4  ft.  of  galvanized  iron  flashing,  12"  wide 
Fastenings  for  windows,  doors,  and  shutters  as  de- 
sired 


238 


The  Sweet  Potato 


Paint 

For  three  coats  outside.    4  gallons 
Nails 

4  pounds  2od 

17  pounds  lod 

85  pounds  8d 

10  pounds  6d 

3  pounds  8d  finish 

If  it  is  desired  to  build  a  house  of  2,500  bushels,  the 
same  general  plans  as  shown  in  Fig.  22,  a  to  f,  may  be 
used.  Here,  too,  the  floor  ventilators  should  be  of  the 
trap-door  type  (Fig.  22,  d  and  e). 


Bill  of  Materials  for  a  2500-BusHEL  House 

DIMENSIONS    20'0"X40'0".       CAPACITY,    ABOUT    2,500 
BUSHELS 

Quantities  are  for  dimensions  shown  on  drawings  and 
should  be  altered  if  dimensions  are  changed.  Footings 
should  be  carried  below  frost  line  or  to  solid  ground. 

Concrete 

Mixture — One   (i)   part  Portland  cement,  three 
(3)    parts   sand,   and   five    (5)    parts   gravel   or 
broken  stone ;  or  one  ( i )  part  Portland  cement  and 
six  (6)  parts  bank-run  gravel. 
Quantities  for  Concrete 


Constit- 
uents 

Walls 

Piers 

or 

Constit- 
uents 

Walls 

Piers 

Cement. 

Sand. 

Gravel. 

79     sacks 
8.7  cu.  yds. 
14.5  cu.  yds. 

7  sacks 
21  cu.  ft. 
34  cu.  ft. 

Cement. 
Bank-run 
gravel. 

79  sacks 
igcu.yds. 

7     sacks 
1.8  cu.  yds. 

Requirements  of  Storage  Houses    239 

Chimney 
500  bricks 

Mixture  for  mortar.  One  ( i )  part  Portland  Cement, 
three  (3)  parts  sand 
Cement  3  sacks;  sand,  10  cu.  ft. 
1-6"  T.  C  thimble 
18  lin.  ft.  8"X8"  T.  C  flue  lining 

Lumber 
Girders 

2-6"  X 10"  X 16' o" 

i-6"Xio"X8'o" 
Sills 

24-2"X8"Xi2'o" 
Studs 

26-2"X4"Xi8'o"  (size) 

3-2"X4"Xi8'o"   (over  windows^ 

i2-2"X4"Xi8'o"  (ends) 

i-2"X4"Xi6'o"  (ends) 

2-2"X4"Xi2'o"  (ends) 

4-2"X4"Xio'o"  (ends) 

i-2"X4"Xi2'o"  (over  doors)' 
Plates 

24-2"X4"Xio'o"  (sides) 

i2-2"X4"Xio'o"  (ends) 
Rafters 

44-2"X6"Xi4'o" 

2-i"X6"Xi2'o"  (ridge)' 

2-i"X6''Xio'o" 
Joists 

62-2"  Xio"Xio'o" 

160  lin.  ft.  i"X3"  Bridging 
Sheeting  (includes  20  per  cent  waste) 

2,568  feet  B.  M.  i"X6"  (roof) 

1,032  feet  B.  M.  i"X6"  (ceiling) 

1,200  feet  B.  M.  i"X6"  (inside  walls) 


240  iThe  Sweet  Potato 

1,344  feet  B.  M.  i"X6"   (outside  walls) 
960  feet  B.  M.  i"X6"  (subflooring) 

Drop  Siding  (includes  20  per  cent  waste) 
1,344  feet  B.  M.  i"X6"  Drop  siding 

Flooring  (includes  25  per  cent  waste) 

1,075  feet  B.  M.  i"X4",  T.  &  G.   (ceiling) 
1,400  feet  B.  M.  i"X4",  T.  &  G.  (walls) 
1,000  feet  B.  M.  i"X4",  T.  &  G.  (floor) 

Ventilators  in  roof 
2-i"Xi2"Xi4'o"S.4S 

Trim 
9-i5^"X4j^"Xi4'o"  S.  4  S.  (windows  and  doors) 
4-iJ^"X4j^"Xi8'o"  S.  4  S.  (corners) 
4-i^"X4j^"Xi4'  o"  S.  4  S.  (end  fascia) 
i2-i"X8"Xio'o"  S.  4  S.  (baseboard) 
4-i"X6"Xi2'o"  S.  4  S.  (ridge) 
4-i"X6"Xio'o"  S.  4  S.  (ridge) 
170  lin.  ft.  ii^"X2>^"  S.  4  S.  (drip  molding) 

Bins 

29-2"X4"Xi8'o"  (studs) 
io-2"X2"Xi8'o"  (nailing  strips) 
20-i"X6"Xi2'o"  (ties  at  partition) 
20-i"X6"Xi6'o''  (ties  at  partition) 
32-i"X2"Xi8'  o"  (cleats  for  loose  boards) 
8-2" X6"  X 10'  o"  ( over  bins) 
i8-2"X4"Xi2'  o"  (under  removable  floors) 
4i8-i"X4"Xi6'o"  (slats  for  bin  sides) 
72-i"X4"Xi6'o"  (slats  for  removing  floors) 
i62-i"X4"Xi6'o"  (loose  slats) 

Screens  (for  cellar  windows) 
3-M"X2"X  16' o"  S.  4S. 

Battens  ( for  shutters  and  doors) 
8-i"X6"Xio'o" 

Platforms 

5-2"X8"Xi2'o"  (sides  and  floor) 
i-2"X8"Xi4'o"  (sides) 


Requirements  of  Storage  Houses    241 

2-2"Xi2"Xi2'o"  (carriages) 

2-4"X4"Xi2'o"  (posts) 

2-2"X4"Xi2'o"  (nailing  strip) 

3-2"X4"Xi4'o"  (joists) 

2-2"Xio"Xi4'o"  (treads) 
Roof  Covering 

Covering  as  desired  for  area  of  1,070  sq.  ft. 
Building  Paper 

58  squares 

Miscellaneous 

6  cellar  frames  and  sash  for  3  lights  8"Xio"  glass 
6  double-hung  sash  and  frames  for  12  lights  9"Xi2" 

glass 
2  No.  2  glazed  doors  3'  o"X/  o",  6  lights  8"Xio" 

glass 
2  door  frames,  for  glazed  doors,  3'  o"X7'  o" 
8  pair  2^"X2>^"  galv.  hinges  for  ventilators  and 

cellar  sash 
8  pair  6"  galv.  T.  hinges,  for  shutters  and  battened 

doors 
2  pair  3>4"X3>^"  loose  pin  butts,  for  glazed  doors 
22"  window  pulleys,  in  ventilator 
2  screw  eyes 
22"  cleats 
24  feet  j^"  rope 

4-^X3"  bolts  with  4"  rings  for  floor  ventilators 
30  lin.  ft.  j4  mesh  galv.  wire  cloth,  ventilators  and 

cellar  screens 
24-^X18"  bolts,  nuts,  and  washers  for  foundations 
6  lin.  ft.  galv.  flashing  12"  wide,  for  chimney 
4-^4X25^"  wrought-steel  straps,  for  platform  posts 
S-}i"Xs"  lag  screws 
Nails 

2  pounds  3od 

10  pounds  2od 


242  The  Sweet  Potato 

30  pounds  lod 
300  pounds  8d 
100  pounds  6d 
10  pounds  8d  finish 

Paint 

For  three  coats  outside.  8  gal. 

Latches  for  doors,  windows,  shutters,  and  cellar  win- 
dows as  selected 


The  Five-Thousand-Bushel  Unit  House 

The  greatest  difficulty  in  storing  sweet  potatoes  is 
met  with  in  large  houses  with  capacities  ranging  from 
10,000  to  100,000  bushels  of  sweet  potatoes.  In  such 
houses,  the  losses  from  rots  are  often  very  heavy.  For 
the  South  especially,  the  5000-bushel  unit  house  is  ad- 
vocated because  in  that  unit  of  bulk  it  is  possible  to 
make  use  of  all  the  natural  conditions  of  ventilation 
and,  with  proper  management,  to  reduce  the  losses  from 
rots  to  a  minimum. 

Where  storage  capacity  of  10,000  bushels  is  desired, 
two  units  of  5000  bushels  each  day  may  be  used.  These 
can  either  be  built  separately  or  the  building  made 
twice  as  long.  In  the  latter  case  one  end  wall  is  saved, 
which  reduces  the  cost  of  the  building,  and  the  wall 
separating  the  two  units  can  be  built  more  cheaply,  con- 
sisting of  a  layer  of  building  paper  and  shiplap  on  each 
side  of  the  studding  instead  of  two  layers  of  shiplap. 
Where  the  houses  cannot  be  built  end  to  end,  they 
should  be  altogether  separated,  a  space  of  not  less  than 
twenty  feet  being  left  between  them.  The  5000-bushel 
unit  is  26'X59'  io"Xii'  4",  the  house  being  consider- 
ably longer  than  wide.  This  is  done  in  order  to  take 
advantage  of  the  maximum  amount  of  ventilation. 


Fig. 


Unit  House. 


a.  to  g.  Photos  showing  the  Texas  A.  and  M.,  5000-bushel-unit  house  for 
sweet  potato  storage,  a.  Exterior  view  of  the  house.  b.  Inside  view 
showing  ceiHng  and  door  vents,  c.  Interior  view  of  upper  and  lower  bins. 
d.  Side  aisle  trap  door  ventilators,  e.  Mitldle  aisle  trap  door  ventilators.  /.  Stove 
and  flue.     g.  Front  gate  of  lower  bin,  showing  how  potatoes  are  taken  out. 


Requirements  of  Storage  Houses    243 

The  unit  house,  also  known  as  the  Texas  A.  and  M. 
House,  is  well  suited  for  Southern  conditions.  The 
house  is  built  of  lumber  for  the  reason  that  this  is  the 
easiest  building  material  to  secure,  and  the  average  car- 
penter can  build  it.  The  house  is  constructed  on  piers 
which  extend  about  two  feet  above  ground.  This  ar- 
rangement allows  the  necessary  floor  ventilation,  which 
is  a  distinct  feature  of  this  type  of  house.  To  protect 
the  house  against  various  severe  cold  spells,  outer  drop 
doors  on  the  north  and  west  sides  reaching  from  the 
base  board  to  the  ground,  are  desirable.  These  are 
raised  or  lowered  as  the  weather  conditions  demand. 
They  are,  however,  merely  an  extra  precaution  against 
cold  spells. 

The  arrangement  of  floor  ventilators,  windows,  and 
ceiling  ventilators  (Fig.  22,  a  to  e)  is  a  distinct  feature 
of  the  house.  Any  or  all  of  these  may  be  opened  or 
closed  when  necessary,  thereby  creating  air  currents 
through  any  part  of  the  house. 

A  special  and  important  feature  of  this  house  is  the 
method  of  heating  and  air  circulation,  which  is  ac- 
complished by  means  of  a  stove  and  flue  (Fig.  22,  f). 
This  is  really  an  adaptation  from  the  modern  system  of 
heating  school  houses  (see  p.  213).  The  feature  of  this 
system  of  heating  is  an  opening  under  the  stove  through 
which  the  outdoor  air  from  under  the  house  enters. 
The  air  then  passes  around  a  jacketed  stove  where  it  be- 
comes heated  and  dried  in  contact  with  the  stove.  It 
then  rises  to  the  ceiling  and  spreads  to  all  parts  of  the 
house,  finally  reaching  the  floor  where  it  escapes 
through  the  bottom  openings  of  the  flue.  By  this 
method  a  constant,  strong  circulation  of  warm  dry  air 
can  be  maintained  whenever  damp  or  cold  weathei; 
makes  its  appearance. 


244 


The  Sweet  Potato 


Bill  of  Material 
Dimensions  26'X59'  io"X  ii'  4".    Capacity  5000  Bushels 

HOUSE  ONLY 


Material 

Size 

Reguired 

Piers 

As 

Detailed 

40 

Platform  Posts 

As 

Detailed 

8 

Chimney  Base 

As 

Detailed 

I 

Sills,  Floor 

6"  XI 2" 

120  Ft. 

9"Xi2" 

180  Ft. 

Joists,  Floor 

.V'xi2"  • 

14'  0" 

55 

Wall  Stops 

2"X4" 

22'  0" 

70 

Cupola  Studs 

2"X4" 

16'  0" 

12 

Plate  Wall 

2"X4" 

16'   0" 

24 

Plate,  Cupola 

2"X4" 

10'  0" 

12 

Requirements  of  Storage  Houses    245 


Bill  of  Material — Continued 
HOUSE  only — Continued 


Material 

Size 

Required 

Joists,  Ceiling 

2"X4" 

14'  0" 

30 

Tires  Over  H. 

2"X4" 

16'  0" 

30 

Rafters,  H. 

2"X6" 

18'  0" 

64 

Rafters,  Cu, 

2"X4" 

16'  0" 

12 

Shiplap 

Floor 

* 

3,500  Yds. 

CeiHng 

3.600 

Walls,  Inside 

.  4,800 

Walls,  Outside 

2,800 

Roof 

2,400 

Building  Paper 

1,600 

Drop  Siding 

No.  117 

2,000 

Shiplap 

Siding 

i"Xio' 

1,100 

Con.  Window  Sill 

2"X6" 

16'  0" 

12 

Shingles 

16,000 

246 


The  Sweet  Potato 


Bill  of  Mate;rial — Contimied 
HOUSE  only — Continued 


Material 

Size 

Required 

Windows 

4  Light 

I5"X30" 

If  Check 

Rail  and  Lock 

16 

Gable  Sash 

4  Light 

I0"XI2" 

2 

Sash  Weight 

32 

Common  Brick 

4,500 

Heater 

Strap  Hinges 

6" 

200 

PuUeys 

I"        • 

6 

Rope 

100  Ft. 

Paint 

2  Coats 

Nails 

400  Pounds 

Bridging 

i"X4" 

640  Ft. 

Load.  Plat. 

4"Xio" 

20'  0" 

2 

2"X  6" 

8'   0" 

40 

Steps 

See  Detail 

Requirements  of  Storage  Houses    247 

Bill  op  Material — Continued 

BIN  MATERIAL 


Material 

Size 

Required 

Studding 

2"X6" 

16'   0" 

52 

2"X6" 

12'  0" 

78 

Bin  Joists 

2"X6" 

16'  0" 

96 

Slats 

i"X6" 

16'  0" 

1,100  Pc. 

Spacers 

2"X4" 

16'  0" 

20 

l"X2" 

16'  0" 

50 

Shiplap 

Stove  Aisle 

i"X6" 

16'  0" 

24 

Nails 

200  Pounds 

Hinges 

6" 

164 

248  The  Sweet  Potato 

Bill  of  Material — Continued 

PLATFORM  FOR  STORAGE   OF   HAMPERS   OR  CRATES 


Material 

Size 

Required 

Post  marked  P  or 

Plans 

2"X6" 

12"  0" 

40 

Slats 

' 

l"X4" 

16'   0" 

200 

Platform 

Joists 

2"X8" 

16'   0" 

25 

Nails 

Bridging 

i"X4" 

400  Ft. 

\The  Medium-Sized  House 

A  15,000-bushel  house  may  be  constructed  for  the 
South,  as  advocated  by  the  United  States  Department  of 
Agriculture.  Here  too,  however,  the  small-sized  hole 
vents  should  be  replaced  by  the  trap-door  system  of  floor 
ventilators  as  advocated  for  the  Texas  A.  and  M.  house 
(Fig.  22,  d  and  e).  A  more  desirable  method  would 
be  to  construct  three  5000-bushel  units,  built  end 
to  end  or  separated  20  feet  from  each  other.  For 
northern  conditions,  a  15,000-bushel  house  may  be  con- 
structed of  three  floors,  with  the  Texas  A.  and  M. 
house  as  a  basis.  In  this  case,  the  house  is  built  on  a 
solid  wall  foundation  instead  of  piers.  Here  one  or  two 
revolving  fans  placed  at  intervals  in  the  house  will  help 
to  create  better  air  currents  during  damp  weather.    Un- 


A 

B 

A 

B 

A 

B 

A 

B 

C 

D 

C 

0 

C 

D 

C 

D 

C 

D 

C 

D 

C 

D 

C 

D 

A 

B 

A 

B 

A 

B 

A 

B 

Fig.  23.     Mr.THOD  of  Loading  and  Fir.r.iN-o  the  FTouse. 

a.  Diagram  showiiii;  urranuement  of  bins  for  lilliiii,'.  (For  explanation,  soe 
p.  236.)  h.  Sliding  trough  connecting  two  floors  and  used  to  lower  hampers 
of  sweet  potatoes  from  the  upper  to  the  lower  door,  [ireventing  unnecessary 
handling  and  bruising,  c.  Outside  platform  conveniently  attached  to  the 
window  and  used  to  load  or  unload  sweet  potatoes  from  two-story  houses. 


Requirements  of  Storage  Houses    249 

der  these  conditions,  an  air  pipe  should  be  connected 
from  the  outside  to  the  stove.  The  moist  air  in  con- 
tact with  the  warm  stove  will  become  dry  before  being 
diffused  through  the  house. 

With  the  large  capacity  houses,  structures  of  two  to 
three  stories  (Fig.  25,  a  and  b)  possess  considerable 
advantage.  There  is  an  economy  in  space,  in  material, 
and  in  fuel.  They  are,  however,  more  difficult  to 
handle  and  to  keep  dry. 

The  mistake  is  frequently  made  of  building  several 
sweet  potato  houses  together  (Fig.  26,  b).  With  such 
an  arrangement  it  is  difficult  to  rid  the  houses  of  the 
inside  moisture.  There  are  very  few  of  the  really  large 
commercial  houses,  especially  those  of  20,000  to  100- 
000-bushel  capacity,  that  are  giving  satisfaction.  The 
reason  may  be  attributed  to  the  difficulty  in  keeping 
them  dry.  Those  who  contemplate  building  large  houses 
should  adopt  the  Texas  A.  and  M.  house  plans  (Fig. 
22,  a  to  g).  In  the  South,  the  house  is  raised  on  piers, 
and  in  the  colder  states,  built  on  solid  wall  foundations 
with  bottom  windows  for  ventilation. 


Bill  of  Material  * 
dimensions   40'-o"xloo.     capacity   about    i5,500 

BUSHELS 

Quantities  are  for  dimensions  shown  on  drawings  and 
should  be  altered  if  dimensions  are  changed.  Footings 
should  be  carried  down  below  frost  line  or  to  solid 
ground. 

*  Prepared  by  the  oflSce  of  Public  Roads  and  Rural 
U.  S.  Dept.  of  Agriculture. 


250 


The  Sweet  Potato 


Concrete 

Mixture — One  part   ( i )    Portland  cement,  three 
(3)   parts  sand,  and    five    (5)    parts    gravel    or 
broken  stone ;  or  one  ( i )  part  Portland  cement  and 
six  (6)  parts  bank-run  gravel. 
Quantities  for  concrete. 


Walls 

Piers 

Cement 

185      sacks 
21.0  cu.  yds. 
34.5  cu.  yds. 

34      sacks 
4.0  cu.  yds. 
6 . 5  cu.  yds. 

Sand 

Gravel 

or 

Walls 

Piers 

Cement 

185      sacks 
44.0  cu.  yds. 

34      sacks 

8.0  cu.  yds. 

Chimney 
1,700  bricks 
Mixture  for  mortar — One  ( i )  part  Portland  cement, 

three  (3)  parts  sand 
Cement,  10  sacks;  sand,  2  cu.  yds. 
36  lin.  ft.  8"X8"  T.  C.  flue  lining 
6-6"  T.  C.  thimbles 

Lumber 
Girders 

6-6"Xio"Xio' 

i4-6"Xio"Xi6' 

i-6"Xio"Xi4' 
Sills 

35-2"X8"Xi6' 
Studs 

62-2"X6"Xi8'  (sides) 


Requirements  of  Storage  Houses    251 

9-2"X6"Xi8'  (over  windows) 

22-2"X6"Xi8'  (ends) 

20-2"X6"Xio'  (ends) 

2-2"X6"Xi2'  (over  doors) 
Plates 

52-2"X6"Xi2'  (sides) 

i6-2"X6"Xio'  (ends) 
Bin  Posts  under  Purlins 

36-2"X4"Xi6' 

24-2"X4"Xi4' 
Purlins 

24-2"X6"Xl2'0" 

i2-2"X6"Xio'o" 
Braces  under  Purlins 

i2-2"X6"Xi4' 
Rafters 

i3C>-2"X6"Xi2' 

i3C-2"X6"Xi4' 

i2-i"X6"Xio'  (ridge) 
Joists 

202-2"Xl0"Xl2' 

ioi-2"Xio"Xi8' 

800  lin.  ft.   i"X3"   (bridging) 

Sheeting  (includes  20  per  cent  waste) 
11,870  feet  B.  M.  i"X6"  (roof) 
5,280  feet  B.  M.  i"X6"   (ceiling) 
2,920  feet  B.  M.  i"X6"  (inside  walls) 
3,450  feet  B.  M.  i"X6"  (outside  walls) 
4,800  feet  B.  M.  i"X6"  (subfloor) 

Drop  siding  (includes  20  per  cent  waste) 
3,400  feet  B.  M.  i"X6"   (siding) 

Flooring  (includes  25  per  cent  waste) 

5,500  feet  B.  M.  i"X4",  T.  &  G.  (ceiling) 
3,440  feet  B.  M.  i"X4",  T.  &  G.  (walls) 
5,000  feet  B.  M.  i"X4",  T.  &  G.   (floor) 


252  The  Sweet  Potato 

Trim 

22-i>^"X4]^"Xi4'  S.  4  S.  (windows  and  doors) 

5-i>^"X4^"Xi8'  S.  4  S.  (corners) 

8-i>^"X45^"Xi2'  S.  4  S.  (end  facia) 

24-i"X8"Xi2'  S.  4  S.  (base  boards) 

i8-i"X6"Xi2'  S.  4  S.  (roof  ridge) 

350  lin.  ft.  iys"X2y2"  S.  4  S.  drip  molding 
Ventilators  in  roof 

6-i"Xi2"Xi4"  S.  4  S. 
Dividing  partitions 

8-2"X4"Xio'  (plates) 

8-2"X4"Xi8'  (studs) 

8-2"X4"Xi6'  (studs) 

i2-2"X4"Xi4'  (studs) 

8-2"X4"Xi2' .(studs) 

8-2"X4"Xio'  (studs) 

2-2"X4"Xi2'  (over  doors) 

2,655  feet  B.  M.  i"X4"  T.  &  G. 

Flooring  (includes  25  per  cent  waste) 
Screens  at  cellar  windows 

9-M"X2"Xi6'  S.  4  S. 
Bins 

72-2"X4"Xi8'  (studs) 

2i-2"X2"Xi8'  (nailing  strips) 

Ties  at  partitions 

"^     \,(S%,(S  %  with   i8's  and   i6's  with 

21-1  X6"Xi6'  ,  . 

42-i"X6"Xio'J  ^^ 

ii8-i"X2"Xi8'  (cleats  for  loose  boards) 

42-2"X6"Xi2'  (over  bins) 

2i-2"X6"Xio'  (over  bins) 

77-2"X4"Xi2'  (removable  floors) 

2,i66-i"X4"Xio'  (slats  for  bin  sides) 

ii4-i"X4"Xi2'  (slats  for  bin  sides) 

66-i"X4"Xi2'  (slats  for  removable  floors) 


Requirements  of  Storage  Houses    253 

462-1  "X4"X  10'  (slats  for  removable  floors) 
i,o83-i"X4"Xio'  (loose  slats) 
Battens  for  shutters  and  outside  doors 

22-l"X6"XlO' 

Platform 

8-2" X4"X  10'  (nailing  strips) 

3-2"Xi2"Xi4'  (carriages) 

4-4"X4"Xi2'  (posts) 

i-2"X8"Xi4'  (sides  and  flooring) 

28-2"X8"Xio'  (sides  and  flooring) 

io-2"X4"Xi4'  (joists) 

3-2" X 10" X 14'  (treads) 
Building  paper 

230  squares 

Roof  Covering 

Covering  as  desired  for  area  of  4,950  sq.  ft. 

MiscellaneoiM 

18  cellar  frames  and  sash,  for  3  lights  8"Xio"  glass 
18  double  hung  sash  and  frames  for  12  lights  9"Xi2" 

glass 
4  glazed  doors  No.  2,  s'X?',  6  lights  8"Xio"  glass 
4  frames  for  glazed  doors,  3'X7'X6"  studs 
4  frames  for  doors  3'X7'X4"studs 
24  pr.  2^"X2J^"  glav.  hinges  for  ventilators  and 

cellar  windows 
26  pr.  6"  galv.  T.  hinges  for  shutters  and  battened 

doors 
4  pr-  3j^"X3/^"  loose-pin  butts  for  glazed  doors 
6-2"  window  pulleys  in  ventilator 
6  screw  eyes  in  ventilators 
6-2"  cleats 
100  lin.  ft.  ji"  rope 

24-^ "X3"  bolts,  with  4"  rings  for  floor  ventilators 
no  sq.  ft.  j4"  mesh  galv.  wire  cloth,  for  vents  and 

cellar  screens 
5o-^"Xi8"  bolts,  nuts,  and  washers  for  foundation 


254  The  Sweet  Potato 

40  lln.  ft.  galv.  flashing  12"  wide,  around  chimney 
8-34"X2^"  wrt.  steel  straps  for  platform  posts 
16-^ "X3"  lag  screws 

Latches  for  doors,  windows,  shutters,  and  cellar  win- 
dows to  be  as  desired 
Nails 

12  lbs.  30d 

25  lbs.  2od 

'jy  lbs.  lod 

930  lbs.  8d 

190  lbs.  6d 

30  lbs.  8d  finish 
Paint 

For  three  coats  outside.    20  Gal. 

Large  Houses 

The  larger  houses  include  the  commercial  type  with 
an  average  capacity  of  30,000  to  100,000  bushels.  Such 
houses  are  located  mainly  around  Swedesborough,  New 
Jersey,  and  a  few  in  Delaware  and  Virginia.  '  In  these 
large  houses  the  problem  in  successful  storage  is  a  diffi- 
cult one.  This  is  mainly  due  to  the  lack  there  of  proper 
means  of  ventilation.  Here  too,  however,  the  difiiculty 
might  be  overcome  to  a  certain  extent  if  the  heating  and 
ventilation  are  arranged  in  a  fashion  somewhat  similar 
to  that  advocated  for  the  Texas  A.  &  M.  house.  Fur- 
thermore, some  system  of  artificial  ventilation  may  be 
necessary,  especially  during  the  damp  warm  weather. 
This  could  be  provided  by  installing  one  or  more  oscil- 
lating fans  to  suit  the  particular  condition  and  needs  of 
the  house. 

Patent  Houses 

The  so-called  patent  systems  aim  at  curing  sweet  po- 
tatoes through  artificial  fanning.    In  the  large-capacity; 


Fig.  24.     Brick  Houses. 
a.   15,000-bushel  sweet  potato  brick  house,     b.  Same  capacity  as 
a    but  lower  nof)r  built  in  brick,  upper  in  lumber,     c.  and  d.    Iwo 
types  of  small   H)(H)-bushel  sweet  potato  houses  lackmg  proper  roof 
and  side  ventilation. 


Requirements  of  Storage  Houses    255 

houses,  the  losses  from  rot  are  often  considerable.  This 
is  brought  about  by  the  difficulty  of  supplying  the  neces- 
sary ventilation  fast  enough  to  remove  the  excess  of  ac- 
cumulated indoor  moisture.  In  this  case,  artificial  ven- 
tilation secured  by  means  of  fans  may  be  very  desirable. 
Simple  as  this  may  appear,  curing  sweet  potatoes  by 
means  of  artificial  ventilation  has  not  even  passed 
through  the  experimental  stage.  While  there  are  many 
artificial  systems  of  curing  sweet  potatoes,  none  are  as 
yet  based  on  carefully  worked-out  scientific  principles. 
Each  new  system  derives  its  birth  from  some  modifica- 
tion of  other  systems.  This  striving  is  bound  to  pro- 
mote the  industry,  yet  the  unsuspecting  public  should 
beware  of  unscrupulous  patentees  who  are  in  the  busi- 
ness to  bleed  the  industry  white.  It  is  not  intended  here 
to  reflect  unfavorably  on  the  honest  inventor.  Yet  we 
must  still  beware  of  those  patentees  who  claim,  for  in- 
stance, that  they  can  cure,  in  twenty-four  hours,  sweet 
potatoes  with  any  kind  of  disease  on  them.  Science  has 
proved  that  this  cannot  as  yet  be  done.  Black  rot,  for 
instance,  is  the  most  persistent  disease,  and  no  amount 
of  artificial  fanning  with  ordinary  warm  air  will  eradi- 
cate it.  On  the  other  hand  every  honest  attempt  at  f  ur- 
theiing  the  sweet  potato  industry  should  receive  the 
support  of  the  public,  and  state  and  federal  institutions. 
At  present  there  are  several  known  patent  systems  of 
curing  sweet  potatoes.  It  is  difficult  to  see  how  a  patent 
on  a  fan  to  send  air  into  a  potato  house  can  have  much 
value,  and  it  is  still  more  difficult  to  see  the  right  to 
charge  an  exorbitant  price  for  it.  Almost  any  one  with 
a  mechanical  bent  of  mind  could  install  some  form  of 
fanning  device.  However,  it  would  be  safe  not  to  in- 
vest in  any  elaborate  scheme  of  artificial  curing  unless  it 
is  first  carefully  worked  out  and  proved  to  be  scien- 


256  The  Sweet  Potato 

tifically  sound.  Moreover,  the  cost  of  construction,  the 
cost  of  operation,  and  the  overhead  running  expenses 
should  be  carefully  considered. 


Types  of  Patent  Houses 

There  are  four  types  or  systems  of  artificial  curing. 
These  are  located  principally  in  Arkansas  and  in  Texas. 


The  Bradley  System 

With  this  system,  the  potatoes  are  cured  by  means  of 
a  series  of  short  3X3  ft.  fans,  mounted  on  a  line  shaft 
elevated  about  10  feet  high,  and  extending  through  the 
entire  length  of  the  building.  There  are  usually  two 
lines  of  shafts,  one  in  each  aisle.  One  end  of  the  shaft 
projects  to  a  bearing  mounted  upon  a  post  a  few  feet 
from  the  wall,  to  which  shaft  a  band-driven  wheel  is 
attached  to  a  thirty-horse-power  gasoline  engine.  The 
heat  necessary  for  curing  is  furnished  by  wood-burning 
stoves  placed  at  various  intervals  in  the  aisles. 

The  building  is  180  by  24  feet  and  holds  16,000 
bushels.  The  wall  is  18  inches  thick,  double,  with  a  dead 
air  space  between,  and  14  feet  high.  The  sills  rest  on 
a  brick  foundation  which  extends  entirely  around  the 
full  length  and  width  of  the  building.  The  studdings  are 
of  2-by-6-inch  scantling,  14  feet  high,  ceiled  on  the 
inside,  weather-boarded  and  filled  with  sawdust.  The 
overhead  joists  or  ties  are  of  the  same  dimensions  as  the 
studding,  and  are  ceiled  on  the  top  only.  The  roof  is 
supported  by  rafters  2-by-6-inches  by  14  feet,  and 
covered  by  sheeting  and  shingles.  The  doors  and 
windows  are  of  the  same  material  and  thickness  as  the 


Requirements  of  Storage  Houses    257 

walls,  constructed  with  beveled  edges,  making  the  house 
quite  tight  when  closed. 

The  inside  of  the  building  (Fig.  27,  a)  is  divided  into 
nine  compartments  or  rooms,  each  20  feet  wide. 
Each  room  is  divided  into  six  slatted  bins,  three  on  each 
side,  separated  by  a  6-foot  central  aisle.  Each  bin  is 
divided  into  an  upper  and  lower  compartment,  each 
holding  150  bushels  of  sweet  potatoes. 

In  filling  the  house,  the  operator  fills  one  compart- 
ment at  a  time.  The  fire  in  the  stove  in  this  partition 
is  started,  and  the  temperature  during  curing  is  main- 
tained at  about  85  to  90  degrees  F.  To  maintain  a  good 
circulation  in  this  partition,  the  vents  are  opened  wide, 
and  fans  started.  In  order  to  confine  the  dry  and  warm 
air,  a  heavy  canvas  or  blanket  is  placed  between  the  first 
and  second  partitions.  The  canvas  reaches  from  the 
ceiling  to  the  floor,  and  extends  from  one  side  of  the 
building  to  the  other. 

To  cure,  partition  No.  2  is  filled  and  operated  in  the 
same  way  as  partition  No.  i,  and  the  canvas  moved  for- 
ward to  separate  it  from  partition  No.  3.  This 
method  is  continued  until  the  house  has  been  entirely 
filled.  Curing  is  claimed  to  be  effected  about  ten  days 
after  the  last  partition  has  been  filled.  The  fires  in  the 
stoves  are  slackened,  and  the  temperature  is  not  per- 
mitted to  fall  below  45  or  to  rise  above  65  degrees 
F.  All  the  vents,  flues,  windows  and  doors  are 
kept  wide  open  during  moderately  warm  weather,  but 
closed  during  damp  cold  days.  The  shrinkage  from 
curing  is  estimated  at  10  to  15  per  cent.  The  Bradley 
system  has  been  modified  by  sweet  potato  specialists  in 
Arkansas.  The  fans  are  placed  on  a  shaft  running 
lengthwise  in  the  middle  alley,  above  the  compartments, 
and  this  rotated  by  motor  power  (Fig.  21  y  b). 


258  The  Sweet  Potato 

The  Delaware  System 

This  system  was  devised  by  the  Dr.  T.  F.  Manus  and 
the  author  in  19 10.  It  was  installed  in  one  of  the  com- 
mercial storage  houses  in  Seaford,  Delaware,  as  a  re- 
sult of  investigations  carried  out  by  the  Delaware  Ex- 
periment Station,  and  the  United  States  Department  of 
Agriculture.  It  consists  of  a  suction  fan  placed  near  the 
ceiling  and  connected  with  pipes  which  are  variously 
distributed.  An  exhaust  pipe  permits  the  exit  of  the 
foul  air.  The  fresh  air  is  brought  in  through  the  win- 
dows in  the  buildings,  and  this  air  is  heated  inside  by 
means  of  coal  or  wood  stoves  hi  the  house. 

~A  modification  of  this  system  is  described  by  Wicks 
(113).  It  consists  of  a  blower  (instead  of  suction  fan) 
placed  near  the  ceiling,  which  forces  the  air  through  the 
bins  by  means  of  pipes. 

The  Wells  System 

With  this  system,  the  warm  air  is  supplied  by  a  motor- 
driven  fan  (Fig.  27,  g)  placed  in  a  room  adjoining  the 
storage  house  (Fig.  o."],  d).  The  air  pipes  or  flues  are 
placed  on  the  ground  underneath  and  extend  up  through 
the  center  of  each  bin,  to  a  point  one-half  the  height  of 
the  bin  (Fig.  27,  e).  One  stove  is  placed  in  the  engine 
room,  but  none  in  the  storage  house.  During  cold 
weather,  the  house  is  heated  by  small  open  charcoal 
stoves,  which  are  variously  distributed. 

The  Nordin  System 

The  following  is  a  description  of  this  system  by  Nor- 
din (74)  himself.    "I  use  common  blacksmith's  blower 


Fig.  25.     Commercial  Houses. 

c.  and  b.  Two  and  three-storied  .■^o.ooo-bushel  sweet  potato  houses  having 
proper  roof  and  side  ventilators. 


Requirements  of  Storage  Houses    259 

No.  I  for  a  2o'X2o'  house  and  No.  2  or  3  for  the 
2o'X4o'  house.  I  put  them  as  near  to  the  ceiHng  as  I  can 
and  put  my  line  shaft  in  a  small  opening  over  one  of  the 
doors.  The  opening  may  be  made  from  1X4  inch  lum- 
ber which  will  make  an  opening  30  inches  square,  inside 
measurements.  The  engine  must  be  on  the  outside ;  by 
not  using  an  air-cooled  engine  the  boiling  water  from 
the  engine  tank  will  cause  a  dampness  to  rise  which 
will  damage  the  potatoes. 

"Estimate  the  speed  of  engine  so  as  to  run  No.  i  from 
3800  revolutions  per  minute;  No.  2,  2500;  and  No.  3, 
3200.  For  conveying  the  air  throughout  the  building,  I 
use  what  tinners  do  for  "down  sprouting"  or  4  or  5-inch 
piping.  This  is  good  unless  the  air  loses  out  at  the 
joints  or  elbows.  With  the  exception  of  this  objection, 
it  is  by  far  the  best,  for  it  is  easily  handled  and  can  be 
turned  about  in  any  direction  desired.  After  equipping 
my  house  in  this  way,  after  a  day's  digging  I  can  throw 
the  air  right  in  under  the  bins  and  keep  the  air  circulat- 
ing. This  dries  the  dampness  out  and  causes  all  cut  po- 
tatoes to  seal  over  so  that  they  will  keep  better  than 
when  left  alone,  for  they  will  sure  rot  if  this  system  is 
not  used,  and  the  bad  part  of  cut  and  bruised  potatoes  is 
that  they  rot  lots  of  others." 


The  Winfield  System 

A  modification  of  the  Nordin  system  is  that  in  use  at 
Winfield,  Texas.  Instead  of  one  blower,  several  are 
used,  one  under  each  bin.  All  the  blowers  (bellows)  are 
connected  to  a  revolving  shaft  which  is  further  attached 
to  a  belt-moving  wheel  in  the  engine  room  (Fig.  28,  d). 
Each  bellow  terminates  in  an  open  slatted  pipe  extend- 


26o  The  Sweet  Potato 

ing  to  the  center  of  the  bin  (Fig.  28,  ej.  The  engine  is 
kept  outside  of  the  storage  house,  and  heat  is  supplied 
by  fire  stoves  which  are  distributed  in  the  aisles  of  the 
house.  The  house  is  160  by  40  feet,  and  10  feet  high 
with  a  capacity  of  30,000  bushels  (Fig.  28,  b  and  c). 
A  modification  of  the  Wells  system  is  that  known  as  the 
Hugh  Lane.  Here  the  air  goes  through  a  furnace  (Fig. 
2,y,  f )  and  instead  of  coming  out  through  a  terminating 
pipe  in  the  bin  is  forced  by  a  fan  and  let  loose  under  the 
floor,  so  that  the  air  seeps  through  small  openings  in  the 
boards  immediately  under  the  bins. 


The  Woods  System 

Another  system  for  which  a  patent  is  apparently 
pending  is  that  known  as  the  Woods  Improved  Air 
Blast  System  (Fig.  28,  a).  Here  the  bin  is  built  the 
length  of  the  house  and  a  perforated  or  slatted  tunnel 
constructed  in  the  middle.  As  the  potatoes  are  put  into 
the  bin,  the  tunnel  remains  empty,  and  through  this  the 
air  is  blown  in  by  a  blast  system. 

Having  in  mind  that  in  artificial  curing  of  sweet  po- 
tatoes all  that  is  necessary  is  a  fan  and  moderately  dry, 
warm  air,  almost  any  conceivable  system  could  be 
worked  out  that  will  accomplish  this  purpose.  For  any 
system  to  deserve  the  consideration  of  the  practical 
grower  it  must,  of  course,  be  based  on  scientific  prin- 
ciples and  actually  "deliver  the  goods"  irrespective  of 
weather  conditions  or  the  way  in  which  potatoes  enter 
the  storage  house.  Its  cost  of  installation  and  operating 
expenses  must  be  such  that  the  overhead  expenses  will 
not  eat  up  the  profits. 


Fio.  26.     Framk  STurnTRKs. 

a.  Two-story  r5.noo-hiishi'l  sweet  potato  liouso  havincf  proper  side 
ventilators  but  lacking  in  roof  vents,  b.  Three  i.s.ooo-btisliel  potato 
houses  built  together,  r.  Two-story  10,000-bushcl  sweet  potato 
house  lacking  both  roof  ami  side-ventilators. 


Pig.  27.     Patent  Housfs. 

a.  Brarllcy,  or  overhead  mechanical  ventilation  system,  b.  Blower 
driven  by  an  electrical  motor  and  used  in  the  Bradley  house.  ((/  and  b  a.''ter 
Wicks.)  c.  and  d.  Well's  sweet  potato  honse  showinRatr  tiie  main  h(just- and 
d,  the  engine  room.  e.  Drawinjj  of  a  lonKitndin.al  section  of  a  l)in  in  a  Well's 
stora),'e  house  showinj;;  foundation,  main  air  pipe,  perforated  hood  and  bin 
proper.  /.  System  in  which  fan  blows  air  through  hot  furnace  liefore  reaching 
potato  house,  thus  supplying  hot  instead  of  cold  air.  i;.  Showing  fan  driven 
by  motor. 


Requirements  of  Storage  Houses    261 


Improvement  of  Faulty  Potato  Houses 

In  a  sweet  potato  house  in  which  year  after  year 
sweet  potatoes  are  lost  from  either  soft  rot  or  black  rot, 
some  steps  must  be  taken  to  prevent  this  great  waste. 
Before  doing  this  one  must  determine  where  the  source 
of  trouble  lies.  It  is  essential,  of  course,  to  make  certain 
that  the  losses  are  not  due  to  mismanagement.  The  so- 
called  manager  who  knows  very  little  about  sweet  pota- 
toes and  understands  still  less  about  the  management, 
will,  in  the  majority  of  cases,  be  responsible  for  the 
losses  of  the  crop.  In  this  case,  it  is  very  easy  to  blame 
the  potato  house,  which  cannot  defend  itself. 

Granting  that  the  manager  understands  his  business, 
the  next  inquiry  must  center  on  the  house.  From  the 
previous  discussion,  it  is  clear  that  in  houses  in  which 
heavy  losses  of  sweet  potatoes  result  from  soft  rot,  there 
is  invariably  a  lack  of  the  necessary  ventilation  (Fig. 
24,  b,  c  and  d).  This  condition  will  often  be  met  with 
in  a  large-sized  house  which  has  little  or  no  ceiling 
(Fig.  26,  a  and  c),  wall,  or  floor  ventilation.  Here  then, 
all  that  will  be  necessary  is  to  remedy  that  condition. 
Before  making  any  alterations  and  improvements  it 
should  be  carefully  decided  whether  or  not  the  altera- 
tions will  justify  the  expense.  Very  often  a  potato 
house  may  be  so  poorly  constructed  that  its  alterations 
will  cost  more  than  building  a  new  one.  In  this  case,  of 
course,  a  carpenter  should  be  consulted.  Where  it  is  de- 
sired to  improve  the  ventilation  of  the  house,  it  would 
be  well  to  adopt  the  ventilation  system  as  advocated  for 
the  Texas  A.  and  M.  house  (Fig.  22,  a  to  f). 

Frequently  many  sweet  potatoes  rot  in  a  potato  house 
that  is  loosely  constructed.  In  such  a  case,  potatoes  are 
subjected  to  chilling  during  cold  weather,  and  more  at- 


262  The  Sweet  Potato 

tention  in  that  direction  will  often  remove  the  source  of 
trouble.  Very  often,  the  heating  system  is  faulty,  in 
which  case  the  heaters  either  produce  an  excessive  heat 
which  makes  it  very  difficult  to  rapidly  lower  the  tem- 
perature, or  it  may  be  that  not  sufficient  heat  is  fur- 
nished at  the  desired  time,  in  which  case,  the  potatoes 
become  chilled  and  consequently  rot.  No  one  method 
of  heating  could  apply  to  all  houses.  In  this  case,  the 
manager  of  the  house  with  a  questionable  heating  sys- 
tem should  consult  his  local  tinsmith,  or,  if  possible, 
some  expert  who  understands  his  business  well. 

In  houses  where  many  sweet  potatoes  are  lost  from 
black  rot,  and  very  little  from  soft  rot,  it  would  seem 
to  indicate  that  the  potatoes  receive  too  much  heat.  In 
this  case,  the  house  is  possibly  provided  with  more 
heaters  than  necessary  or  a  high  temperature  is  main- 
tained during  too  long  an  interval.  The  manager,  by 
using  a  little  judgment,  will  be  able  to  detect  the  cause 
of  these  difficulties  and  will  try  to  avoid  them. 

Management.  We  are  not  mistaken  in  our  belief  that 
a  fool-proof  house  can  never  be  devised.  With  poor 
management,  potatoes  may  be  ruined  in  the  best  of 
houses.  On  the  other  hand,  good  results  will  often  be 
obtained  in  poor  houses  where  common  sense  has  been 
resorted  to.  Having  a  good  house,  and  a  well  worked- 
out  heating  system,  we  should  next  give  attention  to 
the  careful  management  of  that  house.  The  following 
directions  may  serve  as  a  guide : 

During  curing,  the  house  should  be  closed,  except  the 
flue  ventilators  and  the  ceiling  ventilators.  This,  of 
course,  holds  true  only  in  cases  where  the  weather  is 
damp  or  the  outside  temperature  is  below  60  degrees  F. 
At  that  time  a  constant  fire  should  be  maintained  and 
the  temperature  watched  so  that  it  does  not  go  below  60 


Fig 


Patent  Houses. 


a.  Drawin.L;  showinj,'  system  of  the  Woofls  sweet  potato  house  f^.-,  courtesy 
of  the  inventor,  Mr.  E.  M.  Woods),  h  and  c.  Sweet  potato  house  ventilated 
by  means  of  bellows  which  are  run  1)\-  a  gasoline  motor,  showing  at  /;  the 
storage  house;  at  c.  the  engine  room."  d.  vShaft  which  connects  the  motor 
and  the  bellows,  e.  Inner  view  of  l)in  in  b,  showing  the  bellows  and  termi- 
nation of  air  pipe  in  the  bin. 


Requirements  of  Storage  Houses    263 

degrees  or  above  75  to  80  degrees  F.  In  case  the 
weather  is  dry  and  warm  and  the  outside  temperature 
ranges  from  60  to  80  degrees  F.,  a  big  fire  in  the  stove 
is  not  necessary.  Instead,  all  windows,  ventilators,  and 
doors  should  be  wide  open,  and  the  curing  allowed  to 
take  place  through  the  aid  of  the  natural  air  currents. 
The  thing  to  remember  during  curing  is  not  to  permit 
sudden  fluctuations  of  temperature.  That  is,  it  should 
not  be  permitted  to  fall  below  60  degrees  or  rise  above 
80  degrees  for  any  length  of  time.  In  this  direction  one 
should  rely  closely  on  the  thermometers  and  hygrometers 
and  guide  himself  accordingly.  After  the  curing  period, 
the  house  should  be  maintained  at  about  55  degrees  F. 
and  never  be  permitted  to  go  below  40  degrees  or  above 
60  degrees.  During  cool  and  dry  weather,  with  the 
outside  temperature  registering  55  to  60  degrees  F.,  no 
fear  should  be  entertained  as  to  giving  the  house  all  the 
ventilation  possible.  However,  if  the  weather  is  rainy 
and  the  air  damp  and  cold,  everything  should  be  closed 
except  the  flue  and  ceiling  ventilators,  and  a  small  fire 
maintained  so  as  to  prevent  the  potatoes  from  freezing. 
During  very  cold  weather,  when  it  is  difiicult  to  main- 
tain a  temperature  of  50  to  55  degrees  F.,  the  house 
should  be  closed  altogether  and  enough  fire  maintained 
to  keep  up  the  above  temperature.  Should  the  house 
at  any  time  become  wet  and  saturated  with  moisture 
(this  will  be  indicated  by  the  reading  of  the  hygro- 
meter), a  fire  should  be  maintained  with  enough  venti- 
lators open  to  keep  down  the  temperaure  to  about  50 
to  55  degrees  F.,  and  the  relative  humidity  of  the  air 
about  60  to  70  per  cent. 


CHAPTER  XX 

MARKETING 

Marketing  usually  begins  with  digging  and  contin- 
ues all  through  the  season  into  the  winter  months.  The 
greatest  profits  are  of  course  made  when  potatoes  reach 
the  market  during  the  winter  months.  There  are  two 
methods  employed  in  the  large  growing  districts  for 
selling  and  distributing  the  products.  One  is  to  market 
direct  from  the  field  and  the  other  to  store  for  winter 
demands.  Good  profits  are  generally  made  when  sweet 
potatoes  are  marketed  very  early;  however,  little  is  to 
be  expected  when  the  crop  is  dumped  on  the  glutted 
market  during  digging  time.  In  marketing  direct  from 
the  field,  it  is  usually  customary  to  dig,  sort,  pack,  and 
market  all  in  the  same  day.  Here  the  potatoes  are 
graded  into  primes,  seconds,  and  culls,  the  latter  being 
fed  to  stock.  The  first  two  grades  are  usually  shipped 
in  hampers  and  hauled  direct  to  the  railroad  station. 
In  this  case,  there  are  buyers  who  are  well  posted  on 
market  quotations  and  who,  upon  inspection,  generally 
buy  the  potatoes  from  the  wagons.  On  a  large  platform 
near  the  railroad  station  the  potatoes  are  then  repacked 
from  the  hampers  into  barrels  which  are  loaded  direct 
in  the  cars  and  immediately  rolled  to  the  market.  The 
barrels  employed  are  second-hand  flour  barrels  (Fig. 
29,  c).  They  are  usually  split  open  at  various  places 
to  permit  ventilation.  About  200  barrels,  approxi- 
mately 600  bushels,  make  a  carload.  In  New  Jersey 
264 


Marketing 


265 


it  is  customary  to  ship  in  barrels  while  other  sweet 
potato  centers  prefer  to  ship  direct  in  J^-bushel  ham- 
pers (Fig.  29,  d).  George  Livingston,  Chief  of  the 
United  States  Bureau  of  Markets,  in  a  recent  circular 
letter  from  which  we  draw  liberally,  states  that  the 
Bureau  of  Markets  does  not  recommend  the  shipment 
and  sale  of  sweet  potatoes  by  the  weight  per  bushel. 
It  believes  in  the  sale  by  weight  or  by  the  standard 
package.  The  table  of  the  weights  per  bushel  in  various 
states  for  sweet  potatoes  will  indicate  the  folly  of  any 
attempt  to  sell  by  the  bushel.  These  weights  per  bushel 
vary  from  46  to  60  pounds. 

Legal  Weights  per  Bushel  for  Sweet  Potatoes 
(Pounds) 


Alabama 55 

Arkansas 50 

Connecticut 54 

Florida 56 

Georgia 55 

Idaho 50 

Illinois 50 

Iowa 50 

Indiana 50 

Kansas 50 

Kentucky 55 

Maine 54 

Maryland 60 


Massachusetts. . .  54 

Michigan 56 

Minnesota 55 

Mississippi 54 

Missouri 56 

Nebraska 50 

Nevada 50 

New  Hampshire.  54 

New  Jersey 54 

New  Mexico ....  50 

New  York 54 

North  Carolina. .  54 

North  Dakota. . .  46 


Ohio 50 

Oklahoma 55 

Pennsylvania.  ...  54 
Rhode  Island ....  54 
South  Carolina. . .   50 

South  Dakota 46 

Tennessee 50 

Texas 55 

Vermont 54 

Virginia 56 

West  Virginia 50 

Wisconsin 54 


It  will  be  noted  also  that  no  difference  has  been  made 
between  the  weight-per-bushel  of  fresh  and  kiln-dried 
sweet  potatoes. 

The  Bureau  of  Markets  does  believe  in  the  ulti- 
mate establishment  of  standard  containers  to  be  used 
in  shipping  and  marketing  sweet  potatoes,  whether  the 
potatoes  are  sold  by  the  bushel  weight  or  package. 


266  The  Sweet  Potato 

Containers.  The  style  of  container  used  in  the  mar- 
keting of  sweet  potatoes  will  depend  on  market  require- 
ments. For  curing  sweet  potatoes  the  crate  is  undoubt- 
edly preferable,  but  for  the  early  marketing  of  fresh 
potatoes  the  hamper  or  round  basket,  if  well  built,  may 
prove  more  desirable.  In  order  to  prevent  misunder- 
standings, disputes  and  possibly  litigation,  the  different 
types  or  styles  of  containers  should  have  the  same  cu- 
bical contents.  The  bushel-crate  or  basket  of  2150.42 
cu.  inches  is  now  In  general  use  In  certain  sections  of 
the  South  and  East.  Unfortunately,  however,  other 
sizes,  either  slightly  larger  or  smaller  than  the  bushel, 
are  also  in  common  use.  There  Is  an  opportunity  for 
either  the  %-bushel  hamper  or  the  12X12X18"  crate 
to  be  mistaken  for  a  standard  bushel. 

In  standardizing  containers  it  is  axiomatic  that  where 
more  than  one  size  is  adopted,  the  variation  in  size 
should  be  sufficient  to  prevent  deception.  If  a  bushel- 
crate  of  2150  cu.  inches  is  too  small  for  the  economic 
handling  of  sweet  potatoes  owing  to  package  costs,  then 
the  i}^  bushel-crate  containing  3225.6  cu.  inches  is  sug- 
gested as  a  possible  solution.  This  crate  will  cost  but 
a  few  cents  more  than  the  bushel-crate,  holds  approxi- 
mately 50  per  cent  more  potatoes,  is  not  too  large  to  be 
conveniently  handled  in  curing  houses  and  cannot  be  con- 
fused with  the  bushel.  It  has  all  the  advantages  of  the 
i2"Xi2"Xi8"  crate  and  none  of  the  objectionable 
features.  It  is  suggested  that  experimental  shipments 
be  made  in  a.  ij4,  bushel-crate,  having  the  inside  di- 
mensions i3"Xi3"Xi9>i"- 

It  is  easy  to  profit  by  the  experience  of  growers  and 
shippers  in  marketing  barrel  lots  of  fruits  and  vege- 
tables. Prior  to  the  passage  of  the  U.  S.  Standard 
Barrel  Act,  business  was  badly  hampered  by  the  lack 


Marketing  267 

of  uniformity  in  the  size  of  barrels.  This  lack  of  uni- 
formity was  brought  about  largely  through  attempts  to 
standardize  the  weight  of  the  contents.  Tennessee  es- 
tablishes 125  lbs.  and  Massachusetts  150  lbs.  as  the 
weight  of  a  barrel  of  sweet  potatoes.  In  other  states, 
either  law  or  custom  demanded  other  weights  per  barrel. 
The  problem  was  eventually  satisfactorily  adjusted 
through  the  enactment  of  the  present  law  providing  for 
a  standard  barrel  of  7056  cu.  inches  for  fruits,  vege- 
tables, and  all  dry  commodities  except  cranberries  and 
limes,  for  which  special  sizes  were  provided. 

The  hamper  and  round-stave  baskets  so  widely  used 
in  the  United  States  may  be  standardized  on  the  basis 
of  the  same  bushel  (2150.42  cu.  in.)  by  the  provisions 
of  a  bill  which  soon  will  be  inroduced  in  Congress  at 
the  request  of  shippers,  package  manufacturers,  and  the 
trade.  The  standard  sizes  provided  by  the  bill  are  Ya 
bushel,  I  bushel,  ij^  bushels,  and  2  bushels.  About 
one  thousand  carloads  of  peaches  were  shipped  from 
Georgia  alone  in  this  round-stave  bushel  basket  in  19 18. 
The  same  basket  is  being  sold  in  several  states  in  the 
marketing  of  sweet  potatoes.  It  is  a  well-known  fact 
that  hundreds  of  carloads  of  sweet  potatoes  are  mar- 
keted annually  in  bushel  hampers. 

Frequently  the  5-peck  (i^  bushel)  packages  are 
taken  for  i -bushel  packages  on  the  market  in  the 
same  manner  that  ^-bushel  packages  masquerade  as 
full-bushel  packages.  This  was  the  reason  that  the 
truck  growers  of  Providence,  R.  I.  abolished  their  5- 
peck  package  and  replaced  it  with  a  bushel  package 
(2150.42  cu.  in.)  standard  by  state  law.  They  found 
it  unprofitable  to  compete  with  products  from  other 
states  shipped  in  4-peck  or  bushel  packages. 

The  bureau  of  markets  believes  in  the  standardiza- 


268  The  Sweet  Potato 

tion  of  packages,  including  the  sweet  potato  crate  (Fig. 
29,  e)  on  the  basis  of  the  volume  bushel  (2150.42  cu. 
in.)  and  its  subdivision  or  multiples.  The  adoption  of 
crates  of  capacity  intermediate  between  i  bushel  and 
lyi  bushels  will  only  lead  to  confusion  and  misunder- 
standing. This  confusion  apparently  already  exists  and 
is  repeatedly  referred  to  in  the  circular  letter.  Inquiries 
have  been  made  concerning  the  use  of  a  i2"Xi2"Xi7" 
crate  on  the  ground  that  it  will  hold  a  weight  bushel 
of  sweet  potatoes. 

Next  to  grading,  the  neatness,  cleanliness,  and  at- 
tractiveness of  the  package  has  much  weight  in  com- 
manding the  highest  price.  Sweet  potatoes  should  never 
be  shipped  in  ordinary  sacks  (Fig.  29,  f),  as  they  be- 
come badly  bruised  when  handled  in  this  way.  When 
shipping  in  barrels,  during  the  last  of  the  summer  or 
in  the  autumn,  the  ordinary  flour  barrels  with  a  burlap 
cover  will  answer  the  purpose.  However,  for  winter 
shipment,  the  double-headed  stave  barrel  or  tight  box 
is  used  (Fig.  29,  c). 

Frequently  the  best  looking  potatoes  are  ruined  in 
transit.  This  is  commonly  due  to  the  fact  that  the  po- 
tatoes are  subjected,  in  the  car,  to  different  temperatures 
from  those  they  have  had  in  the  potato  house.  With- 
out the  necessary  care,  the  fluctuations  of  temperature 
in  the  car  may  be  very  great,  and  in  this  case  the  po- 
tatoes may  either  soft-rot  from  excess  of  heat  and  lack 
of  ventilation  or  they  may  be  chilled  and  subsequently 
rot.  During  cold  weather  the  containers  in  which  sweet 
potatoes  are  shipped  should  be  lined  inside  with  paper 
and  the  cars  provided  with  some  means  of  heating  or 
ventilation  as  the  case  may  require. 

Usually  there  is  very  little  demand  for  the  Yam  t)rpe 
or  Southern  type  of  sweet  potato  in  the  Northern  mar- 


Fig.  29.     Marketing. 

(I.  Method  of  storing'  and  stacking  hampers  in  sweet  potato  house,  b. 
LabeHiiK  hampers  as  they  are  ready  to  leave  for  the  market,  c.  Method  of 
packing  in  barrels,  d.  Hamper  used  for  sweet  potato  storage  and  shipping. 
e.  Grate  used  for  storage  and  shipping.  /.  Sacked  sweet  potatoes  ready  for 
shipping,      i;.   Incorrect  method  of  stacking  hampers  in  storage  house. 


Marketing  269 

kets.  However,  as  soon  as  the  New  Jersey  district  of 
sweet  potatoes  is  exhausted,  dealers  look  to  the  South- 
ern sweet  potato  to  supply  their  markets.  It  should  be 
borne  in  mind  that  dealers  will  not  handle  Southern 
sweet  potatoes  unless  they  are  thoroughly  cured  and 
placed  on  the  market  late  in  the  winter  when  there  is 
a  brisk  demand. 

Care  in  Shipping 

When  sweet  potatoes  are  shipped  during  cold  weather 
and  to  distant  markets,  the  recommendations  as  of  the 
United  States  Department  of  Agriculture  for  the  Irish 
potato  should  be  observed. 

a.  The  car  should  be  provided  with  a  false  floor. 
This  should  be  done  in  order  to  permit  the  air  to  cir- 
culate freely  under  the  load  from  the  end  of  the  car 
and  the  heater  in  the  center.  The  false  floor  should  be 
supported  and  held  in  place  by  two  by  fours,  running 
lengthwise,  and  never  crosswise  of  the  car. 

b.  The  floor  must  be  of  strong  enough  lumber,  so 
that  the  weight  of  the  load  above  will  not  cause  the 
false  floor  to  sag  and  thereby  cut  out  the  circulation 
of  air. 

c.  It  is  also  advisable  to  use  false  side  walls.  These 
should  reach  to  a  point  not  closer  than  six  inches  from 
the  roof  of  the  car  and  yet  must  extend  above  the  top 
of  the  potatoes.  The  object  is  of  course  to  permit  the 
free  circulation  of  air  from  the  top  of  the  car  to  every 
point  around  the  sides  and  ends,  in  the  spaces  between 
the  car  walls  and  the  false  side  walls,  and  between  the 
false  floor  of  the  car  floor.  False  side  walls  are  used 
in  severe,  cold  weather.  During  moderate  weather,  the 
false  side  walls  as  well  as  false  floor,  are  not  always 
essential,  and  the  papering  may  be  dispensed  with.  In 
cold  weather,  paper  is  necessary;  the  bottom  and  sides 


270  The  Sweet  Potato 

and  ends  up  to  the  ceiling  should  be  papered,  even  an 
extra  strip  of  paper  should  be  placed  at  the  junction 
of  the  walls  and  floors  and  at  the  corners.  In 
building  the  false  side  walls,  or  false  floors,  the  space 
between  the  false  walls  and  the  car  walls  should  not 
be  less  than  four  inches  at  the  ends  and  two  inches  at 
the  sides. 

d.  Every  precaution  is  necessary  to  prevent  the  load- 
ing of  potatoes  in  any  part  of  the  car  so  as  to  cut  off 
free  circulation  of  the  heated  air  which  comes  from 
the  stove  up  to  the  ceiling,  out  over  the  top  of  the 
whole  car,  down  at  the  ends  and  back  under  the  false 
floor  to  the  heater.  Moreover,  it  is  also  essential  to 
maintain  a  more  or  less  even  temperature  in  every  part 
of  the  car  to  prevent  the  freezing  of  the  potatoes  at 
the  floor  and  the  overheating  of  those  at  the  top.  The 
temperature  of  the  car  should  be  about  the  same  as  that 
came.  That  is  not  less  than  45  degrees  nor  higher  than 
of  the  sweet  potato  house  from  which  the  potatoes 
60  degrees  F.  If  it  is  difficult  to  maintain  that  tem- 
perature, It  may  be  necessary  either  to  open  the  bunkers 
to  allow  ventilatioi),  or  to  close  them  tight  to  keep  out 
cold  air.  It  is  always  advisable  with  a  large  shipment 
to  send  a  man  who  will  take  charge  of  that  shipment 
and  attend  to  the  fires  and  to  the  ventilation. 

e.  As  with  Irish  potatoes,  if  the  sweet  potatoes  are 
loaded  less  than  three  feet  from  the  center  of  the  car, 
where  the  stove  is  located,  they  should  be  protected  from 
the  direct  heat  of  the  stove  by  a  sheet  of  asbestos  or 
other  nonconducting  material. 

/.  It  is  necessary  to  guard  against  over-loading  the 
car.  Enough  potatoes  should  be  put  in  to  be  consistent 
with  safety. 

g.  The  stove  should  be  set  up  in  the  middle  between 
the  doors  and  fastened  securely  to  the  floor.  An  ordi- 
nary coal  stove  will  answer  the  purpose.     The  stove 


Marketing  271 

pipe  should  be  carefully  wired  in  place.  The  regula- 
tions of  each  railroad  in  this  case  should  be  followed. 
Before  loading,  the  car  is  heated  for  at  least  six  hours. 
This,  however,  is  only  necessary  in  extra  cold  weather. 

h.  Sweet  potatoes  should  never  be  loaded  into  cars 
with  ice  in  the  bunkers. 

i.  Comparatively  short-haul  shipments  of  potatoes 
may  be  made  without  the  use  of  heaters.  This  is  es- 
pecially true  for  shipments  made  in  the  South.  In  this 
case,  however,  high  grade  refrigerator  cars  should  be 
used.  If  there  is  any  possibility  that  the  car  may  have 
to  be  heated  later,  the  space  between  the  false  floor 
should  be  kept  clear  from  all  obstructions  and  the 
ventilation  openings  through  the  ice  bunkers'  bulkheads 
should  not  be  papered  over. 

y.  During  extra  cold  weather  it  is  advisable  to  use 
not  less  than  two  heavy  layers  of  straw  with  alternate 
layers  of  building  paper  for  added  insulation  between 
the  potatoes,  the  false  floor  and  car  walls. 

Shipping  Sv\^eet  Potatoes  Abroad 

Because  of  the  perishable  nature  of  the  sweet  po- 
tato, no  great  effort  has  been  made  in  the  past  to  ship 
potatoes  abroad.  During  the  last  two  years,  however, 
enterprising  shippers  have  successfully  consigned  sweet 
potatoes  to  Canada.  This  was  done  by  taking  the  ex- 
traordinary precautions  of  properly  heating  the  car  un- 
til it  reached  its  destination.  It  has  not,  as  yet,  how- 
ever, been  found  practical  to  ship  sweet  potatoes  to 
Europe.  The  only  attempt  ever  made  was  in  1902, 
when,  according  to  Taylor  (105)  sweet  potatoes  were 
shipped  to  London  and  Paris.  Some  of  the  potatoes 
were  fresh  from  the  field  and  some  were  partially  kiln- 
dried.    This  was  done  as  an  experiment  by  the  United 


272  The  Sweet  Potato 

States  Department  of  Agriculture.  Some  of  the  po- 
tatoes were  wrapped  and  others  were  not.  The  freshly 
dug  potatoes  arrived  in  better  condition  than  those 
which  had  been  kiln-dried.  Taylor,  therefore,  claims 
that  sweet  potatoes  freshly  dug  from  the  fields  could  be 
successfully  shipped  to  London.  Before  one  could  em- 
bark on  such  an  enterprise,  however,  more  experimental 
shipments  would  have  to  be  made  before  its  success 
could  be  definitely  proved.  One  season's  work  on  this 
would  hardly  justify  any  practical  conclusion.  This, 
however,  is  not  the  case  with  dehydrated  or  canned 
sweet  potatoes,  which  are  unaffected  by  shipment,  and 
this  should  open  a  new,  unlimited  industry  to  the  South- 
ern sweet  potato  grower. 

In  order  to  encourage  the  production  of  better  grade 
sweet  potatoes  for  the  market,  all  agricultural  fairs 
should  offer  premiums  for  the  best  grades  exhibited. 
The  following  score  card  is  suggested  by  Wilson  (115). 

Sweet  Potato  Score  Card 

Points 

Uniformity 35 

Smoothness 20 

Trueness  to  type 20 

Freedom  from  blemishes 15 

Size  (marketable  size) 10 

Total 100 


Sweet  Potato  Association  of  America 

The  above  title  is  as  yet  a  myth,  as  no  such  an  or- 
ganization is  in  existence  although  local  and  state  or- 
ganizations are  coming  into  prominence  in  the  United 
States.    The  sweet  potato  industry  will  not  make  rapid 


Marketing  273 

headway  unless  our  growers  organize  In  a  fashion  simi- 
lar to  that  of  the  White  Potato  Association  of  America. 
This  organization  endeavors  to  unite  all  who  are  en- 
gaged in  the  potato  industry  for  purposes  of  mutual 
protection,  and  for  the  promotion  of  the  potato  industry 
in  all  its  branches.  The  White  Potato  Association  of 
America  further  tries  to  make  the  potato  more  popu- 
lar for  table  use  through  careful  grading  and  packing, 
thus  insuring  better  prices  to  the  grower.  It  further 
tries  to  utilize  all  surplus  potatoes,  to  manufacture 
starch,  potato  flour,  dried  potatoes,  and  all  other  manu- 
factured products.  It  also  tries  to  collect  and  distri- 
bute the  best  available  Information  on  both  the  practical 
and  scientific  phases  Involved  in  increased  yields  coupled 
with  decreased  cost.  Finally,  this  association  tries  to 
increase  the  per  capita  consumption  of  potatoes  from 
2.6  bushels  to  lo  or  12  bushels  where  it  should  be. 

With  reasonable  prices  for  cured  sweet  potatoes  as- 
si^red,  the  sweet  potato  growers  cannot  afford  to  work 
singly  and  single-mindedly.  The  sooner  a  Sweet  Po- 
tato Association  of  America  is  organized  with  aims  and 
purposes  such  as  that  of  the  White  Potato  Association 
of  America,  the  more  rapidly  will  the  sweet  potato  take 
a  place  such  as  the  white  potato  is  now  occupying. 
If,  for  some  unexplained  reason,  a  national  organization 
cannot  be  effected  immediately,  it  could  at  least  begin 
local  and  state  associations.  It  is  doubtful  if  the  sweet 
and  the  white  potato  if  increased  to  their  maximum 
production  will  ever  compete  with  each  other.  Each 
of  these  two  crops  have  distinct  uses  and  possibilities 
untold,  as  a  food  and  for  numerous  commercial  manu- 
facturing purposes. 


BIBLIOGRAPHY 

(i)  Barre,  H.  W.  "Report  of  Botanist  and  Plant  Patholo- 
gist." South  Carolina  Agr.  Expt.  Sta.  23d  Ann.  Rpt. 
:23-39,  1909-10. 

(2)  Barre,  H.  W.    "Sweet  potato  rots."    South  Carolina  Agr. 

Expt.  Sta.  24th  Ann.  Rpt.  :49-Si,  1911. 

(3)  Berger,   E.   W.     "Termite  injury  to   sweet  potatoes." 

State  Plant  Board  of  Florida.  Quarterly  Bui.  2:190-191, 
1917. 

(4)  Blakslee,  a.  F.    "  Heterothallism  in  bread  mold,  Khizopus 

nigricans."     Bot.  Gaz.  43:415-418,  1907. 

(5)  Blakslee,  A.  F.,  and  Gortner,  R.  A.    "On the  occtirrence 

of  a  toxin  in  jtiice  expressed  from  the  bread  mould, 
Rhizopus  nigricans  (Mucor  stolonifer)."  Biochem.  Bui. 
2:542-544,  1913. 

(6)  Bureau  OF  Chemistry.    "Sirup  from  sweet  potatoes,  new 

use  for  siirplus  tubers."  V.  S.  Dept.  of  Agr.  Weekly 
News  Letter  :6,  1919. 

(7)  Burnett  F.  H.    "Sweet  potatoes."    La.  Agr.  Expt.  Sta. 

Bui.  30  (second  series)   :io88,  1894. 

(8)  Carver,  J.  W.     "Saving  the  sweet  potato  crop."    Alabama 

Agr.  Expt.  Sta.  Tuskegee  Bui.  10:5-14,  1906. 

(9)  Carver,  J.  W.     "Possibilities  of  the  sweet  potato  in  Macon 

Co.,  Ala."     Tuskegee  Normal  and  Inds.  Inst.  Ala.  Bui. 

17:5-19,  1910. 
(10)  Chester,  F.  D.    "The  black  rot  of  the  sweet  potato, 

Ceratocystis  fimhriata,   E.    and   Hals."    Delaware   Agr. 

Expt.  Sta.  Third  Ann.  Rpt.  :g<y-9i,  1890. 
(i  i)  Chester,  F,  D,     "The  treatment  of  plant  diseases  in  1896." 

Delaware  Agr.  Expt.  Sta.  Bui.  34:21-22,  1897. 

(12)  Chittenden,  F.  H.    "The  sweet  potato  weevil  and  its 

control."     U.  S.  Dept.  of  Agr.  Bui.  1020:3-24,  1919. 

(13)  Cook,  Mel.  T.,  and  Taubenhaus,  J.  J.    "Trichoderma 

274 


Bibliography  275 


Koningi,  the  cause  of  a  disease  of  sweet  potatoes." 
Phytopath.  1:184-189,  1911. 

(14)  Daugherty,    Chas.    M.    "Foreign   crops,    March-April, 

1913."     U.  S.  Dept.  of  Agr.  Bur.  of  Statistics,  Circ.  47, 

1913. 

(15)  DuGGAR,  J.  F.    "Sweet  potatoes,  culture  and  uses."     U.S. 

Dept.  of  Agr.  Farmers'  Bui.  26:1-30,  1897. 

(16)  DuGGAR,  J.  F.,  and  Williamson,  J.  T.    "Local  fertilizer 

experiments  with  sweet  potatoes."    Alabama  Agr.  Expt. 
Sta.  Bui.  184:19-34,  191 5. 

(17)  Dtjggar,  B.  M.    Fungous  diseases  of  plants,  1909.    Ginn 

and  Company,  New  York. 

(18)  Elliot,  J.  A.    "The  sweet  potato   'soil  rot'  or  *pox' 

organism."    Science,  n.  s.  44:709-710,  1916. 

(19)  Elliot,  J.  A.    "The  sweet  potato  'soil  rot'  or  'pox,'  a 

slime  mold  disease."    Delaware  Agr.  Expt.  Sta.   Bui. 
114:1-25,  1916. 

(20)  Elliot,   J.   A.    "Nematode  injury  to  sweet  potatoes." 

Phytopath.  8:169,  1918. 

(21)  Elliot,  J.  A.     "Storage  rots  of  sweet  potatoes."    Arkansas 

Agr.  Expt.  Sta.  Bui.  144:3-12,  1918. 

(22)  Ensign,    M.    R.    "Sweet    potato    mosaic."    Phytopath. 

9:180,  1919. 

(23)  FiTZ,  James.    Sweet  potato  culture :    84-85, 1886.  Orange 

Judd  Co.,  New  York. 

(24)  Garcia,    Fabian.    New    Mexico    Agr.    Expt.    Sta.    Bui. 

70:5-35,  1909- 

(25)  GoNZALO,  Flor  de  Liza  Merino.    "Sweet  potato  num- 

ber," the  Philippine  Agriculturist   and  Forester   3:148, 
1914. 

(26)  Groth,  B.  H.    "The  sweet  potato,"  Contributions  Bot. 

Lab.  Univ.  of  Pennsylvania  4:1-104,  1911. 

(27)  Halsted,  B.  D.    "Some  fungous  diseases  of  the  sweet 

potato."    N.  J.  Agr.  Expt.  Sta.  Bui.  76:1-32,  1890. 

(28)  Halsted,  B.  D.,  and  Falrchild,  D.  G.    "Sweet  potato 

black  rot."    Jour.  Mycol.  7:1-11,  1891. 

(29)  Halsted,  B.  D.    "Field  experiments  with  soil  and  black 

rots  of  sweet  potatoes."    N.  J.  Agr.  Expt.  Sta.  12th. 
Ann.  Rpt.  1260-266,  1892. 

(30)  Halsted,  B.  D.    "Sweet  potatoes."    N.  J.  Agr.  Expt. 

Sta.  15th  Ann.  Kept.  :35o-36o,  1894. 


276  Bibliography 


(31)  Halsted,   B.   D.     "Experiments   with   sweet  potatoes." 

N.  J.  Agr.  ExpL  Sta.  17th  Ann.  Rept.    :3i9-327,    1895, 
96. 

(32)  Harter,  L.  L.    "Fusarium  bataiaiis  Woll.  and  not  Nectria 

ipomoeae  Hals,  the  cause  of  the  stem  rot  of  the  sweet 
potato."     Phytopath.  3:68,  1913. 

(33)  Harter,  L.  L.     "Control  of  black  rot  and  stem  rot." 

U.  S.  DepL  of  Agr.  Circ.  114:15-18,  1913. 

(34)  Harter,  L.  L.    "Foot  rot,  a  new  disease  of  the  sweet 

potato."     Phytopath  3:243-245,  1913. 

(35)  Harter,  L.  L.    "Foot  rot  of  sweet  potato."     U.S.Dept. 

of  Agr.  Jour.  Agr.  Res.  1:251-274,  1913. 

(36)  Harter,  L.  L.     "  Notes  on  the  distribution  and  prevalence 

of  three  important  sweet  potato  diseases."     Phytopath. 
5:124-126,  1915. 

(37)  Harter,  L.  L.    "Sweet  potato  diseases."     U.  S.  Dept.  of 

Agr.  Farmers'  Bui.  714:1-26,  1916. 

(38)  Harter,  L.L.    "Sweet  potato  scurf."     U.S.  Dept.  of  Agr. 

Jour.  Agr.  Research  5:787-792,  1916. 

(39)  Harter,  L.  L.     "Storage  rots  of  economic  aroids."     U.  S. 

Dept.  of  Agr.  Jour.  Agr.  Research  6:549-570,  1916. 

(40)  Harter,  L.  L.     "Sweet  potato  diseases."     U.  S.  Dept.  of 

Agr.  Farmers'  Bui.  1059:3-24,  1919. 

(41)  Harter,  L.  L.     "Amylase  of  Rhizopus  tritici  with  a  con- 

sideration of  its  secretion  and  action.     "     U.  S.  Dept.  of 
Agr.  Jour.  Agr.  Research  20:761-786,  1921. 

(42)  Harter,  L.  L.     "Respiration  of  sweet  potato  storage  rot 

fungi  when  grown  on  a  nutrient  solution."     U.  S.  Dept. 
Dept.  of  Agr.  Jour.  Agr.  Research  21:211-226,  1921. 

(43)  Harter,  L.  L.,  and  Field,  Ethel  C.    "A  dry  rot  of  sweet 

potatoes  caused  by  Diaporthe  batatatis."     U.  S.  Dept.  of 
Agr.  Bur.  Plant  Ind.  Bui.  281 :7-38,  1913. 

(44)  Harter,  L.  L.,  and  Field,  E.  C.    "The  stem  rot  of  the 

sweet  potato."    Phytopath  4:279-309,  1914. 

(45)  Harter,  L.  L.,  and  Field,  E.  C.    "Die  Walkenkrankheit 

oder  Stengelfaule  der  Siisskartoflfel."    Zeitschr.  Pflanzen- 
krank.  24:204-207,  1914. 

(46)  Harter,  L.  L.,  and  Field,  E.  C.     (Tillotson.)     "Experi- 

ments on  the  susceptibility  of  sweet  potato  varieties  to 
stem  rot."    Phytopath.  5:163-168,  19x5. 

(47)  Harter,   L.   L.,   and  Weimer,  J.   L.    "Studies  in  the 


Bibliography  277 

physiology  of  parasitism  with  special  reference  to  the 
secretion  of  pectinose  by  RMzopus  triiici."  U.  S.  Depi. 
of  Agr.,  Jour.  Agr.  Research  21:609-625,  1921. 

(48)  Harter,  L.  L.,  and  Weimer,  J.  L.     "Susceptibility  of  the 

different  varieties  of  sweet  potatoes  to  decay  by  Rhizopus 
triiici."  U.  S.  Dept.  of  Agr.,  Jour.  Agr.  Research 
22:511-515,  1921. 

(49)  Harter,  L.  L.,  and  Weimer,  J.  L.    "The  surface  rot  of 

the  sweet  potato."    Phytopath.  9:465-469,  1919. 
(so)  Harter,  L.  L.,  Weimer,  J.  L.,  and  Lauritzen,  J.  I. 
"The  decay  of  sweet  potatoes  produced  by  different 
species  oi  Rhizopus."    Phytopath.  11:279-284,  1921. 

(51)  Harter,  L.  L.,  Weimer,  J.  L.,  and  Adams,  J.  M.  R. 
-" "Sweet  potato  storage  rots."     U.  S.  Dept.  of  Agr.,  Jour. 

Agr.  Research  15:337-368,  1918. 

(52)  Harshberger,  J.  W.    A  text  hook  of  mycology  and  plant 

pathology.  191 7,  P.  Blakiston's  Son  and  Co.,  Phila- 
delphia, Pa. 

(53)  Hasselbring,  H.,  and  Hawkins,  L.  A.    "Physiological 

changes  in  sweet  potatoes  during  storage."  U.  S.  Dept. 
of  Agr.,  Jour.  Agr.  Research  3:331-342,  1915. 

(54)  Hasselbring,  H.,  and  Hawkins,  L.  A.    "Carbohydrate 

transformation  in  sweet  potatoes."  U.  S.  Dept.  of  Agr., 
Jour.  Agr.  Research  5:543-560,  191 5. 

(55)  Hasselbring,   H.,   and   Hawkins,   L.   A.    "Respiration 

experiments  with  sweet  potatoes."  U.  S.  Dept.  of  Agr., 
Jour.  Agr.  Research  5:509-517,  191 5. 

(56)  Hasselbring,  H.    "Behavior  of  sweet  potatoes  in  the 

ground."  U.  S.  Dept.  of  Agr.,  Jour.  Agr.  Research 
12:9-17,  1918, 

(57)  Johnson,  T.  C,  and  Rosa,  J.  T.    "  Sweet  potato  culture." 

Virginia  Truck  Expt.  Sta.  Bui.  19:387-450,  1916. 

(58)  Keitt,    T.    E.    "Sweet   potato   work   in    1908."    South 

Carolina  Agr.  Expt.  Sta.  Bui.  146:3-21,  1909. 

(59)  Lang  worthy,  C.  F.    "Potatoes,  sweet  potatoes  and  other 

starchy  roots  as  a  food."  U.  S.  Dept.  of  Agr.,  States 
Relations  Service  Bui.  468:1-28,  191 7. 

(60)  Learn,  C.  D.    "Black  rot  of  sweet  potatoes."    Oklahoma 

Agr.  Expt.  Sta.  Extens.  Div.  Circ.  10:1-3,  1915. 

(61)  Lauritzen,   J.    I.    "The   relation   of   temperature   and 


278  Bibliography 


humidity  to  infection  by  certain  fungi."  Phytopaih. 
9:1-35,  1919. 

(62)  Manns,  Thos.  F.,  and  Taubenhaus,  J.  J.    "Some  prac- 

tices in  sweet  potato  growing  to  avoid  loss  from  disease." 
The  Delaware  Farmer,  Newark,  Del.  1:5-9,  1914. 

(63)  Manns,    T.    F.     "Sweet   potato   storage   in    Delaware.*' 

Delaware  Agr.  Expt.  Sia.  Bui.  127:9-64,  1920. 

(64)  McClintock,  J.  A.     "Sweet  potato  diseases."     Virginia 

Truck  Expt.  Sta.  Bui.  22:455-486,  191 7. 

(65)  McCormick,  Florence  a.     "Notes  on  the  anatomy  of  the 

yotmg  tuber  of  Ipomoea  batatas."  Bot.  Gaz.  61 :388-398, 
1916. 

(66)  McDonnell,  C.  C.     "The  manufacture  of  starch  from 

sweet  potatoes."  South  Carolina  Agr.  Expt.  Sta.  Bui. 
136:7-50^  1908. 

(67)  Meir,  F.  C.     "Watermelon  stem  end  rot."     U.  S.  Dept. 

of  Agr.,  Jour.  Agr.  Research  6:149-152,  191 6. 

(68)  Melhus,  I.  E.    "Experiments  on  spore  germination  and 

infection  in  certain  species  of  Oomycetes."  Wisconsin 
Agr.  Expt.  Sta.  Research  Bui.  15:25-83,  1911. 

(69)  Miller,  F.  E.     "Sweet  potato  growing."     U.  S.  Dept.  of 

Agr.,  Farmers'  Bui.  999:3-30,  1919. 

(70)  Mooring,    C.    D.     "Sweet    potatoes."    Oklahoma    Agr. 

Expt.  Sta.  Circ.  25:3-12,  1914. 

(71)  Morse,  W.  J.,  and  Shapovalov,  M.    "The  Rhizoctonia 

disease  of  white  potatoes."  Maine  Agr.  Expt.  Sta.  Bui. 
230:193-216,  1914. 

(72)  MuNZOR,  Apolonio  Ramos.     "Identification  and  tests  of 

varieties  of  sweet  potato."  The  Philippine  Agriculturist 
and  Forester  3:127-145,  1914. 

(73)  Newman,  C.  L.     "Sweet  potato  experiments."    Arkansas 

Agr.  Expt.  Sta.  Bui.  72:33-43,  1902. 

(74)  NoRDiN,  J.  Green.     The  sweet  potato,  how  to  grow  and 

keep  it.     50  pages,  191 2,  Russellville,  Arkansas. 

(75)  Orton,  W.  a.     "Potato  diseases  in  San  Joaquin  Coimty, 

California."  U.  S.  Dept.  Agr.,  Bur.  Plant  Indus.  Circ. 
23:14,  1909. 

(76)  OuDEMANS,  C.  A.  J.  A.     "Podromed'tmefloremycologique 

obtenue  par  la  culture  sur  gelatine  preparee  de  la  terra 
humeuse  du  'Spanderswood,'  pers  du  Bussum."  Archiv. 
Neerlandaises  Sci.  Exactes  et  Naturelles.   :29i,  1902. 


Bibliography  279 

(77)  Parloa,    Maria.    "Preparation    of    vegetables    for    the 

table."     U.  S.  DepL  of  Agr.,  Farmers'  Bui.  256:3-46, 
1917. 

(78)  Price,  R.  H.    "Sweet  potatoes."     Texas  Agr.  Expt.  Sia. 

Bui.  28:329-346,  1893. 

(79)  Price,  R.  H.    "Sweet  potatoes."    Texas  Agr.  Expt.  Sta. 

Bui.  36:609-625,  1895. 

(80)  Price,  R.  H.    Sweet  potato  culture  for  profit.     1896  (Dallas, 

Texas). 

(81)  Price,  J.  C.  C.     "How  to  construct  a  flue  heated  hot  bed." 

Alabama  Polytechnic  Inst.  Extension  Circ.  15:2-4,  1918. 

(82)  PRESCOTT,  S.  C.  (Major).      "Dehydration  of  vegetables, 

past,  present  and  future."     The  Potato  Magazine  1:6, 
16-17,  20-22,  1919. 

(83)  Ramsey,  G.  B.     "A  form  of  potato  disease  produced  by 

Rhizoctonia."    Jour.  Agr.  Research  9:421-426,  1917. 

(84)  RoBSON,    W.    "The    classification    of    sweet    potatoes." 

West  Indian  Bui.  12:521-526,  1912. 

(85)  Rosen,  H.  R.    "The  mosaic  disease  of  sweet  potatoes." 

Arkansas  Agr.  Expt.  Sta.  Bui.  167:3-9,  1920. 

(86)  Scott,  John  M.     "Sweet  potato  silage."    Florida  Agr. 

Expt.  Sta.  Press  Btds.  274  and  278,  1917. 

(87)  Starnes,  N.  H.    "Sweet  potato  diseases."    New  Cyclo- 

pedia Amer.  Hort.,  L.  H.  Bailey,  6:1754-1755,   1906. 
New  York. 

(88)  Stevens,  F.  L.    Bot.  Gaz.  38:300,  1904. 

(89)  Stevens,   F.   L.    "Sweet  potato  wilt."    North  Carolina 

Agr.  Expt.  Sta.  Ann.  Kept.    :20-29,  1905. 

(90)  Stevens,  F.  L.    "Report  of  the  biologist."    North  Caro- 

lina Agr.  Expt.  Sta.  Kept.    :i5-i7,  1907. 

(91)  Stevens,   F.   L.     The  fungi  which  cause  plant  diseases, 

Macmillan  Co.,  1913. 

(92)  Stevens,  N.  E.,  and  Wilcox,  R.  B.    "Rhizopus  rot  of 

strawberries  in  transit."     U.  S.  Dept.  of  Agr.  Bui.  531: 
1-22,  1917. 

(93)  Stuckey,  H.  p.    "Sweet  potatoes."    Georgia  Agr.  Expt. 

Sta.  Bui.  107:83-112,  1914. 

(94)  Swingle,  D.  B.     "Formation  of  the  spores  in  the  sporangia 

of  Rhizopus  nigricans  and  of  Phycomyces  nitens."     U.  S. 
Dept.  of  Agr.  Bur.  Plant  Indus.  Bui.  37:9-40,  1903. 


28o  Bibliography 

(95)  Taubenhaus,  J.  J.     "The  black  rots  of  the  sweet  potato," 

Phytopath.  3:159-165,  1913. 

(96)  Taubenhaus,  J.  J.     "Soil  stain  and  pox,  two  Uttle-known 

diseases  of  the  sweet  potato."     (Abstract,)     Phytopath. 
4:405,  1914. 

(97)  Taubenhaus,   J.   J.    "Recent  studies   of  some  new  or 

little-known  diseases  of  the  sweet  potato."    Phytopath. 
4:305-320,  1914. 

(98)  Taubenhaus,  J.  J.     "Some  cultural  methods  of  the  sweet 

potato  to  avoid  field  loss."    Practical  Farmer.  Phila- 
delphia, July,  1 914. 

(99)  Taubenhaus,  J.  J.     "Soil  stain  or  scurf,  of  the  sweet  pota- 

to."    U.  S.  Dept.  of  Agr.,  Jour.  Agr.  Research  5:995-1001, 

1916. 
(100)  Taubenhaus,  J.  J.    "Pox  or  pit  (soil  rot)  of  the  sweet 

potato."     JJ .   S.    Dept.    of   Agr.,   Jour.    Agr.    Research 

13:437-450,  1918. 
(loi)  Taubenhaus,  J.  J.     "Field  diseases  of  the  sweet  potato 

in  Texas."     Texas  Agr.  Expt.  Sta.  Bui.  249:3-22,  1919. 

(102)  Taubenhaus,  J.  J.     "Recent  studies  on  Sclerotium  rolfsii 

Sacc."     U.    S.    Dept.    of    Agr.,    Jour.    Agr.    Research 
18:127-138,  1919. 

(103)  Taubenhaus,  J.  J.,  and  Manns,  T.  F.    "The  diseases  of 

the  sweet  potato   and  their  control."    Delaware  Agr. 
Expt.  Sta.  Bui.  109:3-55,  191 5. 

(104)  Taubenhaus,  J.  J.,  et  al.     "Storage  and  diseases  of  the 

sweet  potato  in  Texas."     Texas  Agr.  Expt.  Sta.  Bui. 
250:5-41,  1919. 

(105)  Taylor,  W.  A.     "Fniit  and  vegetable  storage  and  ship- 

ment experiments  of  the  U.  S.  Dept.  of  Agr."     Virginia 
State  Hort.  Soc.  Rept.    •.i']-2g,  1902. 

(106)  Thomson,  H.  C.    "Sweet  potato  storage."     U.  S.  Dept.  of 

Agr.  Farmers^  Bui.  970:3-27,  1918. 
(1060)   Thomson,  H.  C.  and  Beattie,  J.  H.     "  Sweet  potato 
storage  studies."     U.S.  Dept.  of  Agr.  Bui.  1063:1-18, 
1922. 

(107)  TowNSEND,  C.  O.     "Some  diseases  of  the  sweet  potato 

and  how  to  treat  them."    Maryland  Agr.  Expt.  Sta.  Bui. 
60:147-168,  1899. 

(108)  Waite,  B.  M.     "Sweet  potato  culture."    Rept.  Maryland 

Agr.  State  Hort.  Soc.  5:54-60,  1920. 


Bibliography  281 

(109)  Weimer,  J.  L.    "Reduction  in  the  strength  of  the  mercuric 

chloride  solution  used  for  disinfecting  sweet  potatoes." 
U.  S.  Dept.  of  Agr.,  Jour.  Agr.  Research  21:575-587,  1921. 

(110)  Weimer,  J.  L.,  and  Harter,  L.  L.     "Glucose  as  a  source 

of  carbon  for  certain  sweet  potato  storage  rot  fungi." 
U.  S.  Dept.  of  Agr.,  Jour.  Agr.  Research  21:189-210, 
1921. 
(ill)  Weimer,  J.  L.,  and  Harter,  L.  L.  "Respiration  and 
carbohydrate  changes  produced  in  sweet  potatoes  by 
Rhizopus  tritici."  U.  S.  Dept.  of  Agr.,  Jour.  Agr. 
Research  21:627-635,  1921. 

(112)  Weimer,  J.  L.,  and  Harter,  L.  L.    "Wotmd-cork  forma- 

tion in  the  sweet  potato."     U.  S.  Dept.  of  Agr.,  Jour. 
Agr.  Research  21:637-647,  1921. 

(113)  Wicks,   W.   H.    "Sweet   potato  culture    in    Arkansas." 

Arkansas  Agr.  Expt.  Sta.  Bui.  124:5-31,  1915. 

(114)  Wilcox,  E.  M.    "Diseases  of  sweet  potatoes  in  Alabama." 

Ala.  Agr.  Expt.  Sta.  Bui.  135:1-16,  1906. 
(lis)  Wilson,  R.   S.    "Agricultural  fairs."    Mississippi   Agr. 

Extension  Bui.  14:3-42,  1919. 
(116)  WoLLENWEBER,    H.    W.    "Identification    of    species    of 

Fusarium    occurring    on    the    sweet    potato,    Ipomoea 

batatas."    U.  S.  Dept.  of  Agr.,  Jour.  Agr.  Research 

2:251-286,  1914. 


INDEX 


Acreage,  5,  6. 
Acromoniella  sp.,  164, 
Actinomyces  chromogentis,  163. 

poolensis,  116. 

Alternaria  rot,  154. 
Aspergillus  niger,  163. 

B 

Barre,  H.  W.,  108,  186. 
Berger,  E.  W.,  173. 
Bibliography,  275. 
Black  Rot,  141, 
Blakslee,  A.  R,  127. 
Blue  stem,  154. 
Botrytis  cinerea,  149. 

rot,  149, 

Bradley  system,  257. 
Burnette,  F.  H.,  160. 


Carver,  J,  W.,  82,  125. 
Cephalothecium  sp.,  163. 
CeratoStoma  sp.,  163. 
Ceratostomella,  fimbriata,  141. 
Charcoal  rot,  159. 
Chittenden,  F.  H.,  167. 
Cold  frame,  19. 
Cook,  M,  T.,  148, 
Construction     of     commercial 

curing  houses,  229. 
Cost  of  production,  61. 
Cottony  rot,  160. 
Cultivation,  59. 
Culture,  level,  39, 

ridge,  39. 

Curing,  care  after,  218. 
^ period,  199. 


283 


C ysto  pus    ipomoeae-pandu- 

ranae,  120. 
Cystospora  batata,  107. 


Daugherty,  C.  M.,  6. 
Dead  hills,  41. 
Dehydration,  179. 
Diaporthe  batatatis,  136. 
Diplodia  tubericola,  145. 
Disease  losses,  105. 
Distribution,  4. 
Dry  rot,  136. 

Duggar,  J.  F.,  37,  iii,  112,  122, 
160. 


Economic  importance,  4. 
Elliott,  J.  A.,  io8,  no,  112,  IIS, 

141,  217. 
Ensign,  M.  R.,  165. 
Epicocum  rot,  159. 
Estabrook,  L.  M.,  6. 


Faulty  houses,  improvement  of, 

262. 
Fertilizer,  chemical,  45-53. 
efifect  on  composition  of 

potatoes,  56. 
Field,  Ethel,  136,  138,  157. 
Filling  the  house,  225. 
Fitz,  J.,  82. 
Flea  beetle,  172. 
Flue-heated  beds,  16. 
Foot  rot,  139. 
Fuligo  violacea,  119. 


284 


Index 


Fusarium  accuminatum,  158. 

batatatis,  154. 

caudatum,  158,  163. 

culmorum,  158. 

hyperoxysporum,  154. 

incarnatum,  158. 

orthoceras,  158. 

oxysporum,  157, 

radicicola,  158. 

solani,  158. 

orthoceras    var.    trisepta- 

tum,  158. 
vasinfectum,  163. 


Garcia,  F.,  10,  59,  60. 
Giberella  rot,  136. 

saubinettii,  136. 

Gonzalo,  R,  7. 
Grades,  U.  S.,  74,  77. 
Grading,  74. 
Groth,  B.  H.,  64,  loi. 
Growing  season,  222. 

H 

Halsted,  B.  D.,  108,  iii,  114, 

121,   122,   125,  136,  151,   154, 

160. 
Harshberger,  J.  W.,  122. 
Harter,   L.   L.,    120,    130,    135, 

136,   138,   139,   140,   141,   149, 

151,    153,   154   157,    158,    159, 

163,  189,  191,  199. 
Hauling,  77. 
Harvesting,  70. 

implements,  72. 

Hasselbring,   H.,   72,   189,    190, 

197,  198. 
Hawkins,  L.  A.,  189,  190,  197, 

198. 
Heterodera  radicicola,  174. 
Hollow  heart,  164. 
Hot-bed,  15. 

care,  22. 

covering,  20. 

soil,  19. 

troubles,  23. 

watering,  21. 


Hot-water  beds,  18, 
Hygrometers,  217. 


Insect  pests,  167. 
Irrigation,  59. 


Java  black  rot,  145, 
Johnson,  T.  C,  7. 

K 
Keitt,  T.  E.,  80,  97. 


Langworthy,  C.  F.,  80. 
Large  houses,  255. 
Lauritzen,  J.  I.,  213. 
Learn,  C.  D.,  108. 
Leidigh,  Mrs.,  Sa. 
Lime,  55. 

M 
Machinery,  41. 
Macrosporium  sp.,  163. 
Manns,  T.  F.,  213. 
Manure,  green,  55. 
Manure-heated  beds,  15. 
Manure,  stable,  53. 
Marketing,  265. 
McCIintock,  J.  A.,  122,  123,  124, 

154. 
McDonnell,  C.  C,  93. 
Medium-sized  house,  249. 
Meier,  F.  C,  145. 
Melanospora  sp.,  163. 
Melchers,  L.  E.,  io8. 
Melhus,  I.  E.,  123. 
Mice  injury,  175. 
Miller,  F.  E.,  4,  18. 
Moisture,  211. 

Monilochaetes  infuscans,  150. 
Mooring,  C.  D.,  40,  213. 
Morphology,  normal,  loi. 
Mosaic,  165. 


Index 


285 


Mucor  racemosus,  135. 
rot,  135. 


N 


[58. 


Nectria  ipomoeae, 
Nelson,  Ray,  165. 
Neosmospora  vasinfectum,  163. 
Net  necrosis,  165. 
Non-parasitic  diseases,  164. 
Nordin  system,  259. 


Origin,  3. 
Orton,  W.  A.,  128. 
Oudemans,  C,  148. 
Ozonium  omnivorum,  161. 


Parloa,  M.,  82. 
Patent  houses,  255. 
Penicillium  sp.,  163. 
Pestalozzia  sp.,  163. 
Phyllosticta  bataticola,  139. 

leaf  spot,  139. 

Physarum  plumbeum,  120. 
Physiological    changes    during 

storage,  189. 
Pit,  107. 

Plenodomus  destruens,  139. 
Powdery  slime  mold,  119. 
Pox,  107. 

Prescott,  S.  C,  180. 
Price,  R.  H.,  7,  16,  19,  20,  63, 

108  126,  211. 
Propagation,  6. 


Ramsey,  G.  B.,  115, 
Rat  injury,  175, 
Rhizoctonia  root  rot,  163. 
Rhisopus  nigricans,  124,  131. 

parasitic  species,  135. 

Ring  rot,  131. 
Robson,  W.,  64. 
Root  knot,  174. 
Rosa,  J.  T.,  7. 


Rotation,  43-45- 


Sclerotium  bataticola,  159. 

rolfsii,  160. 

Score  card,  273. 
Scott,  J.  M.,  92. 
Scurf,  150. 
Seed,  7. 

bedding,  ig. 

certified,  27-33. 

from  vine  cuttings,  12. 

home-grown,  10. 

plat,  8. 

selection,  8. 

stored  and  banked,  11. 

treatment,  24. 

Septoria  bataticola,  147. 

leaf  spot,  147. 

Shapovalov,  M.,  115. 
Shipping  abroad,  272, 

care,  270. 

Small  house,  235. 
Soft  rot,  124. 

susceptible  hosts,  128. 

Soil  preparation,  43. 

requirements,  42. 

rot,  107. 

stain,  150. 

Sphaeronema  fimbriatum,  141. 
Sporotrichium  sp.,  163. 
Sprout  diseases,  26. 
Sprouts,  buying  or  selling,  36. 

drawing  of,  34,  35. 

number  per  bushel,  9. 

Starnes,  N.  H.,  126. 
Steam-heated  beds,  18. 
Stem  rot,  154. 
Stevens,  R  L.,  122,  154. 
Storage,  critical  periods,  220. 

in  banks,  185. 

bins,  227. 

cellars,  186. 

containers,  227. 

house  considerations,  222. 

methods,  179. 

preparing  house,  223. 

Stuckey,  H,  P.,  10,  37,  56,  60, 

62,  215. 
Surface  rot,  157. 


286 


Index 


Sweet  potato  as  food,  79. 

Association,  273. 

canning,  183. 

flour,  182. 

quarantine,    170,    171, 

172. 

recipes,  82-88. 

silage,  92. 

starch,  93. 

syrup,  88. 

uses,  79. 

vine  for  forage,  91. 

weevil,  167. 

Swingle,  D.  B.,  127. 


Taubenhaus,  J.  J.,  8,  36,  108, 
112,  115,  125,  131,  145,  148, 
151,  154,  160. 

Temperature,  199. 

Termite  injury,  173. 

Texas  A.  &  M.  House,  244. 

root  rot,  161. 

The  Unit  House,  243. 

Thermometers,  216. 

Thompson,  H.  C,  68. 

Tools,  transplanting,  40. 

Tortoise  beetles,  173. 

Townsend,  C.  O.,  108,  iii,  160. 

Transplanting,  37. 

Trichoderma  koningi,  148. 

lignorum,  148. 

'rot,  148. 

Trichosporium  sp.,  163. 

Type  of  house,  230. 


Varieties,  63-69. 

susceptible   to    black   rot, 

143- 

pox,  118. 

Rhizopus,  130. 

soil  stain,  153. 

; vine  wilt,  157. 

Variety  classification,  63-69. 

yield,  62. 

Ventilation,  217. 
Verticillium  cinnaharinus,  164. 
Vine  pinching,  60. 
wilt,  154. 

W 

Weimer,  J.  L.,  4,  7,  25, 130,  157, 

189. 
Wells  system,  259. 
White  rust,  120. 
Wilcox,  E.  M.,  108,  125,  160. 
Winfield  system,  260. 
Wollenweber,  H.  W.,  155. 
Wood  ashes,  55. 
Woods  system,  261. 


Yield,  62. 


Zygorhynchus  sp.,  163. 


This  book  is  a  preservation  facsimile. 

It  is  made  in  compliance  with  copyright  law 

and  produced  on  acid-free  archival 

60#  book  weight  paper 

which  meets  the  requirements  of 

ANSI/NISO  Z39.48-1992  (permanence  of  paper) 


Preservation  facsimile  printing  and  binding 

by 

Acme  Bookbinding 
Charlestown,  Massachusetts 


2006 


